Abstract:
Methods, program product, and apparatus are provided for implementing a blood glucose meter that will remind the user to test his or her blood glucose after a programmable wait when a hypoglycemic event is detected. Diabetics frequently have a “rebound” hyperglycemic event (high blood glucose) occur as a result of a hypoglycemic event (low blood glucose). The disclosed invention allows the user to program the meter with a waiting period which he or she determines is appropriate to wait following a low blood glucose reading. At the end of this period, the meter will alert the user by way of an audible or tactile warning.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to blood glucose meters, and in particular, to an inexpensive blood glucose meter that reminds the user to recheck his or her blood glucose after a programmable interval when the meter detects a hypoglycemic event.  
         DESCRIPTION OF THE RELATED ART  
         [0002]    Insulin dependent diabetes mellitus (IDDM) is caused by the autoimmune destruction of the insulin producing islets of Langerhans in the pancreas. Insulin replacement therapy is the interim treatment for IDDM until such time as islet transplants, stem cell treatments, or other improved treatments become feasible. Insulin lowers the concentration of glucose in the blood, while food—in particular, carbohydrates—raises the concentration of glucose in the blood. The challenge of insulin therapy is to administer food and insulin in a manner that maintains blood glucose concentrations in an acceptable range, thereby avoiding hypoglycemia and hyperglycemia.  
           [0003]    Hyperglycemia (high blood glucose concentration) has adverse long-term consequences for the body. These consequences include kidney damage leading to kidney failure, microaneurisms in the retina causing blindness, and the blocking of capillaries in the extremities causing an inability to heal wounds and subsequent gangrene. Hypoglycemia (low blood glucose concentration) has an immediate adverse consequence of reduced brain function that leads to confusion and an inability to reason, remember, or react. In the extreme, hypoglycemia causes seizure, coma, and death.  
           [0004]    The first insulin used by diabetes patients was regular insulin taken from beef or pig pancreases. This insulin lasts for about six hours, so that patients were required to inject it three or four times per day. After World War II, longer acting insulin was developed by binding regular insulin to protamine and zinc. Regular insulin dissociates slowly from protamine and zinc, extending insulin action to twelve hours for intermediate acting insulin and twenty-four hours for ultralente insulin. Patients enjoyed reducing injections to one per day, but were required to modify their eating to a snack-all-day regimen to avoid hypoglycemia. The one daily insulin dose was adjusted as needed to reduce the incidence of both hypoglycemia and hyperglycemia.  
           [0005]    The development of portable blood glucose meters encouraged the development of more sophisticated insulin therapy regimens. One of these regimens is the split/mixed regiment that consists of two daily doses of mixed regular and intermediate acting insulins taken before breakfast and dinner. These four insulin therapy components are adjusted using blood glucose values measured before each meal and at bedtime. Patients using the split/mixed regimen are required to eat substantially the same meals every day so that the four insulin components may be adapted to the consistent meal pattern over time. Patients on the split/mixed regimen are not only faced with a consistent pattern of what they eat in terms of amount of food, but are also required to eat their meals at particular times. Delay of a meal will result in the patient suffering hypoglycemia.  
           [0006]    A more recent development in insulin regimen is the basal/bolus regimen, which provides far more flexibility in quantity and timing of meals. The basal/bolus program attempts to emulate the method by which an intact pancreas controls blood glucose. Normally, the intact pancreas produces a steady supply of basal insulin to accommodate the body&#39;s basic insulin needs for glucose secreted at a relatively constant rate from the liver. The pancreas handles meals by releasing a sharp impulse of bolus insulin to accommodate a rapidly rising blood glucose resulting from transformation of carbohydrates (and, to a lesser extent, other food items, especially protein) into blood glucose.  
           [0007]    In the basal/bolus regimen, the basal insulin releases are emulated by a once a day injection of a long acting insulin, such as Lantus®, a product of Aventis Pharmaceuticals, or Ultralente®, a product of Eli Lilly and Company. Ultralente is sometimes injected twice daily. These long acting insulins provide the body with a relatively constant supply of insulin. The bolus insulin releases are emulated by bolus injections of fast acting Humalog® (lispro), or other fast acting insulin. The amount of fast acting insulin taken in an injection must be proportional to the amount of carbohydrate taken with the meal. Some diabetics are able to further fine-tune the injection by calculating the amount of protein, which has a smaller effect on the rise of blood glucose concentration.  
           [0008]    To illustrate the basal/bolus regimen in an example, assume a typical diabetic who requires 0.5 units per hour of basal insulin. This person will need a 12-unit injection of long acting insulin daily to cover his or her basal requirements. Timing of such an injection is not critical, and in fact, the long acting insulin is often mixed with the fast acting insulin in one of the bolus injections. Further assume that this typical diabetic&#39;s blood glucose is raised 4 mg/dl (blood glucose concentrations are measured in milligrams per deciliter) for every gram of carbohydrate eaten. This is known as carbohydrate sensitivity. Assume also that a unit of insulin (insulin is measured in “units”) reduces this typical diabetic&#39;s blood glucose concentration by 40 mg/dl. This is known as insulin sensitivity. The diabetic sits down at a meal and adds up the total grams of carbohydrates in the meal. Assume the meal consists of 80 g of carbohydrates. The diabetic would compute the increase in blood glucose concentration to be (4 mg/dl/g)*(80 g)=320 mg/dl. The diabetic would then compute the amount of bolus insulin required to accommodate, or “cover” this increase, knowing his or her insulin sensitivity. (320 mg/dl)/(40 mg/dl/unit)=8 units. The diabetic would therefore inject 8 units of fast acting insulin before eating the meal.  
           [0009]    In practice, exercise, stress, and even unknown factors cause the above calculations to be only approximations. The diabetic, in his or her basal/bolus regimen, usually also needs to adjust the bolus dose taken based upon a blood glucose reading taken prior to the meal. A typical desired target for a diabetic&#39;s blood glucose concentration prior to a meal is 100 mg/dl. “Normal” blood glucose concentration range is 80 mg/dl to 120 mg/dl. A blood glucose concentration of 70 mg/dl or lower is usually considered to be hypoglycemic. A blood glucose concentration of 40 mg/dl is dangerously hypoglycemic and the diabetic is usually seriously impaired when his or her blood glucose concentration is at that level. A sustained blood glucose concentration of 20 mg/dl or lower is considered to expose the diabetic to permanent brain damage.  
           [0010]    Suppose that, in the example above, the diabetic&#39;s pre-meal blood glucose concentration were 180 mg/dl. The diabetic would recognize that as being 80 mg/dl above the desired concentration of 100 mg/dl. Using the insulin sensitivity in the example, the diabetic would compute the additional insulin required as (80 mg/dl)/(40 mg/dl/unit)=2 units. In the example, the diabetic would then take a 10-unit bolus; 8 for the carbohydrates in the meal, and 2 more to “cover” the fact that the premeal blood glucose concentration was 80 mg/dl above target. If, in the example, the premeal blood glucose concentration were 80 mg/dl, the diabetic would compute a 0.5 unit negative adjustment, and thus take a bolus of 7.5 units with the meal instead of 8 units.  
           [0011]    Insulin pumps are mechanisms that allow the basal/bolus regimen to be practiced even more effectively. An insulin pump contains a reservoir of fast acting insulin. Insulin is pumped through a tube from the reservoir into the diabetic. A computer within the pump, with which the diabetic interacts, controls the insulin pump. The diabetic programs in a “basal profile” which tells the pump how much of the fast acting insulin per unit time period to infuse into the diabetic. The pump then infuses this amount into the diabetic in a series of small infusions. In the example above, an infusion rate of 0.5 units per hour was assumed. In practice, this number varies considerably from one individual to the next. In some individuals, the rate also needs to vary during the course of a day. In particular, many diabetics find they need a higher rate of infusion for several hours before breakfast. The series of small infusions of fast acting insulin replaces the single injection of long acting insulin as described above. At a meal, the diabetic makes the same calculations described above, and interacts with the pump to cause it to infuse the proper bolus of fast acting insulin to cover the carbohydrates of the meal.  
           [0012]    Methods and apparatus exist to assist the diabetic in the computations described. U.S. Pat. No. 5,822,715, “Diabetes management system and method for controlling blood glucose”, by Worthington, et al, (hereinafter, Worthington), is an example of the art in this field. Worthington describes a system with which the diabetic interacts, entering insulin doses, meal carbohydrate quantities, and measured blood glucose at any particular time. The system uses a measured current blood glucose concentration, insulin absorption characteristics, insulin sensitivity parameter programmed by the user, and a carbohydrate sensitivity parameter entered by the user to compute, at the time of the measurement, whether the diabetic&#39;s blood glucose concentration is above or below where it should be. Worthington&#39;s system then recommends injection or infusion of additional insulin if the blood glucose concentration is too high. If the concentration is too low, Worthington&#39;s system recommends how much additional carbohydrate should be eaten. The system warns the diabetic if the blood glucose concentration is too high or too low.  
           [0013]    Several “continuous metering” products are currently available. One is the Glucowatch®, by the Cygnus corporation, which takes several measurements of a diabetic&#39;s blood glucose (inferred from readings of “interstitial fluid”) per hour. The Glucowatch® has the capability of warning the diabetic when his or her blood glucose concentration is too high or too low. A second such product is the Minimed Continuous Glucose Monitoring System® (CGMS), by the Medtronic Corporation, which takes even more frequent measurements than the Glucowatch®. Currently the CGMS does not alert the diabetic to high or low measurements.  
           [0014]    A phenomena found in many diabetics is hypoglycemic rebound. If a diabetic becomes hypoglycemic, stress hormones will trigger a significant release of glucose that had been stored in the liver. This will cause a hyperglycemic event several hours after the hypoglycemic event. That is, the blood glucose concentration will swing from a low value to a high value, neither of which is healthy for the diabetic. Not every diabetic is subject to hypoglycemic rebounds, but many are. Timing of the hypoglycemic rebound also varies between individuals. One diabetic may find himself or herself to experience a rebound after two hours, while a second diabetic may not have a rebound until four hours after a hypoglycemic event. Furthermore, upon discovering the hypoglycemic event, the diabetic needs to consume some form of carbohydrate to treat the event. The system of Worthington would be valuable for telling the diabetic how much carbohydrate to consume. The diabetic could also do the calculations described above, although many times diabetics&#39; ability to do calculations when their blood glucose concentrations are low is severely impaired. The diabetic might not be able to enter numbers into Worthington&#39;s system in his or her impaired state. The diabetic often takes more than the calculations (or, Worthington) would call for in order to more quickly get their blood glucose concentration out of the hypoglycemic range of values. Such “overtreatment” is another common cause of becoming hyperglycemic some hours after suffering a hypoglycemic event.  
           [0015]    The diabetic frequently forgets to test his or her blood glucose concentration several hours after a hypoglycemic event, and, therefore, often only discovers a very high blood glucose concentration at a pre-meal test, which is often many hours after the hypoglycemic event occurred. Worthington and other prior art do not remind the diabetic to test their blood glucose concentration, following a hypoglycemic event, to check for a rebound or overtreatment hyperglycemic event. The Glucowatch® would provide warnings for both the original hypoglycemic event, as well as a rebound hyperglycemic event. However, the Glucowatch® is large, is expensive to purchase, and requires expensive disposables. The CGMS is also expensive, and requires a sensor to be embedded in the skin. Currently the CGMS does not give warnings for highs and lows, but could easily be modified to do so.  
           [0016]    Therefore, there exists a need for an inexpensive blood glucose meter that reminds the user to test again, after a time interval previously programmed by the user, upon detection of a hypoglycemic event.  
         SUMMARY OF THE INVENTION  
         [0017]    A principle object of the present invention is to provide an improved, inexpensive, blood glucose meter that provides a warning to the user after a predetermined time interval following the meter&#39;s measurement of a blood glucose concentration lower than a predetermined value.  
           [0018]    In an embodiment of the invention, the improved blood glucose meter comprises a memory programmable by the user that stores a time interval, and a blood glucose concentration limit below which a measured blood glucose concentration reading causes the time interval to be loaded into an interval timer and to start the interval timer. When the interval timer indicates that a time period equal to the time interval has elapsed, the meter alerts the user.  
           [0019]    In an embodiment of the invention, the improved blood glucose meter will provide an audible alarm after a time interval, as described above, has expired.  
           [0020]    In an embodiment of the invention, the improved blood glucose meter will provide a tactile alarm after a time interval, as described above, as expired.  
           [0021]    In an embodiment of the invention, a method is described wherein an improved blood glucose meter will start a timer upon measuring a blood glucose concentration lower than a preprogrammed limit, and will produce an audible or tactile alert upon completion of a programmable time interval, to remind the user to recheck his or her blood glucose concentration.  
           [0022]    In an embodiment of the invention, a program product is described wherein the program product when executed in a blood glucose meter, will remind the user to re-check his or her blood glucose concentration after a predetermined interval has elapsed following the blood glucose meter&#39;s measurement of a blood glucose concentration less than a predetermined threshold or limit. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    [0023]FIG. 1 shows a drawing of a blood glucose meter and a blood glucose test strip.  
         [0024]    [0024]FIG. 2 shows a block diagram of a blood glucose meter that implements the current invention.  
         [0025]    [0025]FIG. 3 shows a flowchart of a program executed by the processor in the blood glucose meter that implements the current invention.  
         [0026]    [0026]FIG. 4 shows a flowchart of a portion of a program executed by the processor in the blood glucose meter that implements the current invention. The portion shown prompts the user for information, which is then entered, by the user. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]    Having reference now to the figures, and in particular FIG. 1, a blood glucose meter  100  (hereinafter “meter  100 ”) typically has a case  102  to enclose and protect the internal components. Case  102  is typically made of plastic, but can be any suitable material. A display  104  gives the user information such as prompts for data entry, time and date, a prompt inviting the user to begin a blood glucose concentration test, as well as displaying the measured blood glucose concentration. In the exemplary FIG. 1, current reading  116  displays upon display  104 , and shows an exemplary value of 87. Current time and date  117  is also displayed upon display  104 .  
         [0028]    A set of buttons  106  allows the user to input data to meter  100 , turn meter  100  on or off, or to make inquiries as to previous blood glucose concentration measurements. Meters existing on the market today have widely different button  106  arrangements. Some have two buttons  106 , as shown in FIG. 1. Some, such as described by Worthington, have a relatively large number of buttons  106 . The particular button layout is not important to the current invention, and any pushbutton interface is intended in the scope and spirit of this invention.  
         [0029]    Alarm  107  can be an audible alarm, a tactile alarm that vibrates, or even a blinking light.  
         [0030]    Meter  100  has a slot  108  that receives a blood glucose test strip  110 . Test strip  110  is typically a disposable item that is used for a single blood glucose concentration test and is then discarded. Typically, test strip  110  comprises a reagent area  112  upon which a sample of blood is deposited. Electrical resistance of the reagent in area  112  changes depending upon glucose concentration in the blood sample. Electrodes  114  are exposed at one end of test strip  110  in order to make electrical contact with mating electrodes (not shown) within slot  108 . Each electrode  114  is electrically continuous from the exposed portion to area  112  and is electrically coupled to area  112  such that changes in resistance of the reagent can be measured at electrodes  114 . Test strip  110  is inserted into slot  108  and meter  100  performs resistance measurements as a drop of blood is deposited on area  112 . Meter  100  is designed to determine the blood glucose concentration of the blood sample and display the blood glucose concentration on display  104  in suitable units such as milligrams per deciliter. Other units are used in some countries, and this invention is not dependent upon the particular units used. Meter  100  could alternatively use a reagent that changes color, rather than a reagent that changes resistance. This invention is not dependent on the specific mechanism to determine the blood glucose concentration. The examples discussed are illustrative rather than limiting.  
         [0031]    [0031]FIG. 2 shows a block diagram of a blood glucose showing the meter&#39;s functional components. Processor  202  can be any general or special purpose digital processor that can be suitably programmed to perform the input/output (I/O) needs of the meter, as well as all required computations and control.  
         [0032]    Electrically coupled to processor  202  is a memory  204 . Memory  204  can be any suitable memory such as Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), flash memory, ferroelectric memory, or magnetic memory. Not all portions of memory  204  need be of the same type.  
         [0033]    Program storage  206  holds the executable program used by processor  202  to perform the control and computational steps required for the function of the meter. Program storage  206  can be made of Read Only Memory (ROM), since the program may not need to be changed once written and debugged. Advantageously, however, program storage  206  is implemented in a nonvolatile memory capable of both reading and writing, such as Flash memory or Ferroelectric memory. Such memory allows more flexibility during manufacturing, and would allow for modifying the program after manufacture.  
         [0034]    Most meters on the market store a history of some number of the most recent previous tests, comprising a number of prior blood glucose concentration results, which are also stored in a portion of memory  204  called previous readings  208 . For example, a meter might have enough storage in previous readings  208  to store a history of the last  100  tests of blood glucose concentrations, along with the month, day, and time at which those tests were performed. Some meters have the capability of downloading this history to a computer at the user&#39;s home or at a doctor&#39;s office. Computer analysis of the history can then be performed by the user or the doctor to look for trends or trouble spots in the therapy. Previous readings  208  can be advantageously implemented in nonvolatile memory. Previous readings  208  could also be implemented in volatile memory such as SRAM or DRAM, since only the test history would be lost if the battery (not shown) which powers the meter should fail.  
         [0035]    Calibration data  210  is stored in meter&#39;s memory  204 . The reagent on the test strips can vary slightly from lot to lot during manufacture of the test strips. Most meters have “fine tuning” data shipped with each group of test strips. Some meters provide a semiconductor chip product containing this data in nonvolatile form. This chip effectively becomes calibration data  210  as a memory portion of the aggregate memory  204 . Some meters provide a test strip that contains the calibration data that is inserted into slot  108  of FIG. 1, read by processor  202 , and stored in nonvolatile memory storage as calibration data  210  by the processor  202 .  
         [0036]    Memory  204  further contains program data storage  212 , which is used for temporary storage of numbers needed during calculations and processing by processor  202  as it executes the steps programmed in program storage  206 . Data storage  212  can be implemented in either volatile storage such as SRAM or DRAM or in nonvolatile storage, as described above.  
         [0037]    Memory  204  further contains hypo limit  214 , a number entered by the user to define his or her hypoglycemic limit. The user knows from experience what low blood glucose concentration limit, or threshold, will generally produce a hypoglycemic rebound. As described in more detail below, if a measurement of blood glucose concentration is below the value in hypo limit  214 , the meter will produce an alarm at a programmable time interval thereafter. Hypo limit  214  is preferably implemented with nonvolatile storage so that the user does not have to reenter the value stored in hypo limit  214  if the battery (not shown) powering the meter should fail.  
         [0038]    Memory  204  further contains storage for wait interval  216  that holds a value of time that the meter will wait after measuring a hypoglycemic event, after which an alarm will be actuated, as described in detail below. The user knows from experience when a hypoglycemic rebound will occur following a hypoglycemic event. The user will enter a value into wait interval  216  that is appropriate for the user. Typically, a time of two to six hours would be entered and stored in wait interval  216 .  
         [0039]    Blood glucose sensor  222  is a device that measures blood glucose concentration of a sample of blood. As described above, sensor  222  could measure blood by resistivity measurements of reagent  112 , or color change of reagent  112 , or any other method of determining the blood glucose concentration of a sample of blood. Sensor  222  is electrically coupled to processor  202  so that the blood glucose concentration measurement can be transmitted to processor  202 .  
         [0040]    Keys  106  are electrically coupled to processor  202 . Keys  106  are used to turn the meter  100  on or off, and allow the user to enter data or commands to processor  202 . For example, the values stored in hypo limit  214  and wait interval  216  would be entered on keys  106 , in a conventional manner.  
         [0041]    Alarm  107  is electrically coupled to processor  202 . Alarm  107  could be an audible alarm. Alarm  107  could be a tactile alarm that vibrates or shakes when activated by processor  202 . Alarm  107  could be a visible alarm, implemented with a light emitting diode (LED), an incandescent light, or any other visible means of alerting the user.  
         [0042]    Display  104  is electrically coupled to processor  202 , and communicates information to the user. Information such as date, time, blood glucose concentration, and prompts for data entry are advantageously displayed on display  104 . Display  104  is typically implemented as a liquid crystal display (LCD) but could be an array of LEDs.  
         [0043]    Clock  220  is electrically coupled to processor  202 . Clock  220  is a conventional clock that provides hour/minute, day, and month capabilities. This information is needed to document the time when blood glucose measurements are taken.  
         [0044]    Interval timer  221  is a timing device used to indicate the elapse of time periods. “Egg timers”, and common kitchen timers are examples of interval timers familiar to most people. Interval timer  221  can be initialized to a value. Upon receiving a signal to start, interval timer  221  begins counting. The count may increment or decrement. In one embodiment, interval timer  221  is initialized with the value stored in wait interval  216 . Interval timer  221  is then started in a decrementing mode. Upon the interval timer function reaching a predetermined value, advantageously zero, processor  202  is signaled over the electrical coupling between interval timer  221  and processor  202 . Processor  202  then activates alarm  107  for some predetermined time, or until the user shuts off alarm  107  using keys  106 . As will be appreciated by those skilled in the art, many variants of this mechanism are possible. For example, in a second embodiment, interval timer  221  could be loaded with the value stored in wait interval  216 , be initialized to a predetermined value, advantageously zero, and then be incremented until the counter value equals or exceeds the value loaded from wait interval  216 . In another embodiment, interval timer  221  could be initialized to zero, or other predetermined value, and started counting by processor  202 . Processor  202  periodically would then periodically receive a value from interval timer  221  indicating how much time has elapsed on the timer since it was started. Processor  202  would compare that value with the value stored in wait interval  216 . Processor  202  would then activate alarm  107  when the value from the timer exceeds the value stored in wait interval  216 .  
         [0045]    Interval timer  221  could be implemented as a feature of clock  220 . Many digital clocks also have interval timer functions. Interval timer  221  is shown in the figure as a separate block for clarity.  
         [0046]    [0046]FIG. 3 shows an exemplary flowchart of the steps that are executed by processor  202  under control of the program stored in program  206 .  
         [0047]    Block  302  is the beginning of the process and simply passes control to block  304 . Block  304  initializes interval timer  221  to a predetermined value and makes sure the interval timer  220  is not running. Block  304  passes control to block  306 .  
         [0048]    Block  306  checks to see if the user wants to enter data. Some meters have a special key  106  for this purpose. Some meters with only two keys  106  indicate that the user wants to enter data by pressing both keys  106  simultaneously. If the user does want to enter data, control is passed to block  308 , which receives the user&#39;s data entry. An exemplary set of steps executed by block  308  is shown in FIG. 4. After data has been received from the user in block  308 , or, if no data entry was desired in block  306 , control is passed to block  310 .  
         [0049]    Block  310  checks to see if a measurement, or test, of a blood sample is desired. Most meters begin a test when a strip  110  is inserted into slot  108 , although other meters can and do use other means to signal a beginning of a test. If a test is not desired, control is passed to block  312 ; otherwise, control is passed to block  316 .  
         [0050]    Block  316  is the step in which blood glucose sensor  222  determines the blood glucose concentration and communicates that value over the electrical coupling to processor  202 . Control then passes to block  318 , where processor  202  compares the value of the blood glucose concentration with the value stored in hypo limit  214 . If the value of the blood glucose concentration is less than the value stored in hypo limit  214 , control passes to block  319 ; otherwise control is passed to block  320 .  
         [0051]    In block  319 , processor  202  fetches the value from wait interval  216 , stores the value in interval timer  221 , and activates interval timer  221 . In this example, interval timer  221  decrements. As described earlier, interval timer  221  could also count up from zero to the value in wait interval  216 , as a variant of the implementation described. The scope of this invention includes any timer mechanism for interval timer  221 . The particular details of loading and sensing interval timer  221  will vary depending on the exact mechanism employed. Block  319  passes control to block  320  upon completion.  
         [0052]    In block  320 , processor  202  stores the measured blood glucose concentration, together with the time and date of the measurement, in previous readings  208 . Control then passes to block  321 .  
         [0053]    In block  321 , processor  202  displays the measured blood glucose concentration. Other information such as date and time can also be displayed on display  104 . Control passes then to block  322 .  
         [0054]    Block  322  continues to display the blood glucose concentration on display  104  until the end of the blood glucose test is signaled. The signal could be the withdrawal of test strip  110  from slot  108 . The signal could be driven by a separate counter (not shown) that limits the duration of the test to save battery power. Power saving timeouts are well known in currently available blood glucose meters. Upon end of the blood glucose concentration test, control is passed from block  322  to block  306 .  
         [0055]    Block  312  checks if the time interval initialized in interval timer  221  has elapsed. In the example, block  319  initialized interval timer  221  with the value stored in wait interval  216  and started the timer decrementing. Expiration of the time period specified by the value of the wait interval  216  can be indicated by processor  202  comparing the value of interval timer against a predetermined value, advantageously zero. Some embodiments of interval timer  221  could activate an interrupt signal coupled to processor  202 . If the interval has elapsed, control is passed to block  314 ; otherwise, control is passed to block  306 .  
         [0056]    In block  314 , processor  202  activates alarm  107  for a predetermined time period, or until the user deactivates alarm  107  by using one or more keys  106 , according to the particular implementation&#39;s choice of a deactivation keystroke or keystroke sequence. Block  314  then transfers control to block  304 .  
         [0057]    [0057]FIG. 4 shows an exemplary set of steps by which the user can enter data into the meter.  
         [0058]    Block  402  is the starting block, to which control is passed from block  306  of FIG. 3. Block  402  passes control to block  404 .  
         [0059]    Block  404  prompts the user to enter the present time-of-day hour. This is usually done by displaying “0” on display  104  and incrementing the hour for each push of a key  106 . When the correct hour is reached, the user pushes a different key  106  to verify that the correct hour is displayed. Upon the user&#39;s verification, block  406  stores the hour in storage (not shown) in clock  220 .  
         [0060]    Similarly to blocks  404  and  406  for entering and storing the correct hour, blocks  408  and  410  prompt for, and store, the correct minutes of the current time.  
         [0061]    Additional similar steps (not shown) are usually added to prompt for, and store, month and date information into storage (not shown) in clock  220 .  
         [0062]    Block  412  prompts the user for a value for hypo limit  214 . A zero value would be displayed. This value would be incremented, as described above, each time a key  106  is pushed. When the desired value for hypo limit  214  is displayed, the user would push a different key  106  to verify that the correct hypo limit is displayed. Upon the user&#39;s verification, block  414  stores the value into hypo limit  214 .  
         [0063]    Block  416  prompts the user for a value for wait interval  216 . A zero hour value would be displayed. This value would be incremented, as described above, each time a key  106  is pushed. When the desired wait time is displayed, the user would push a different key  106  to verify that the correct wait time is displayed. Upon the user&#39;s verification, block  416  stores the value into wait interval  416 .  
         [0064]    The routines, or sequences of instructions, executed on processor  202  to implement the embodiments of the invention, are stored in program  206  in memory  204 . These routines are simply referred to as “computer programs”, or simply “programs”. The computer programs typically comprise one or more instructions that are resident in program storage  206 , and that, when read and executed by processor  202 , cause processor  202  to perform the steps necessary to execute steps or elements embodying the various aspects of the invention. Moreover, while the invention has been described in the context of a fully functioning blood glucose meter, those skilled in the art will appreciate that the various embodiments of the invention are capable of being distributed as a program product in a variety of forms that can be written into program storage  206 , and that the invention applies equally regardless of the particular type of signal bearing media used to actually carry out the distribution. Examples of signal bearing media include but are not limited to recordable type media such as volatile and non-volatile memory devices, floppy and  15  other removable disks, hard drives, magnet tape, optical disks, among others, and transmission type media such as digital and analog communication links.  
         [0065]    While the present invention has been described with reference to the details of the embodiments of the invention shown in the drawings, these details are not intended to limit the scope of the invention as claimed in the appended claims.