When your doctor takes your blood pressure, it is expressed as a fraction of two numbers, one on top (systolic) and one on the bottom (diastolic). For instance, 120/80 mm Hg. The top figure represents the amount of pressure in your arteries during heart muscle contraction. This number goes up when you get anxious or tense. The bottom number indicates the level of pressure during heart muscle relaxation. This number tends to be lower when you're relaxed. Both figures are usually needed to report your blood pressure. Your doctor may also ask you about other factors that can affect how your blood vessels constrict and relax, such as food intake, exercise habits, use of medications, etc. They will try to identify any patterns that may help explain your current state of health. Sometimes only one number is reported; this is called an isolated systolic reading. An isolated systolic reading occurs when just one of the blood pressure cuffs is used to take the measurement. If only one cuff yields a high reading, it's important to understand that you have hypertension. However, if both cuffs read high, it could mean that you have lied down when taking the reading or that one of your blood vessels is having trouble communicating with the cuff. In this case, another method must be used to determine which blood vessel is responsible for the elevated reading.