Patient description: The patient is a 24-year-old man who has had type 1 diabetes for 11 years. He presents to the emergency room with hyperglycemia and concern for possible diabetic ketoacidosis after not taking his insulin for 3 days. The patient reports that he is currently homeless and has lost his supply of insulin, syringes, glucometer, and glucose testing supplies. The patient states that at the time of his initial diagnosis with type 1 diabetes he was hospitalized with a glucose value >1000 mg/dL. At the time, he was experiencing polyuria, polydipsia, and polyphagia. He reports that he has been on insulin since the time of his diagnosis, and he has never been prescribed oral agents for diabetes management. Most recently, he has been using insulin glargine 55 units once daily, and insulin aspart sliding scale 3 times daily. The patient has had previous episodes of diabetic ketoacidosis, for which he was hospitalized. With this episode of hyperglycemia, he is not experiencing any nausea, vomiting, or abdominal discomfort, and he appears well. His lab studies showed: A1c: 11.3% Creatinine: 0.9 mg/dL with eGFR >60 mL/min Aspartate aminotransferase (AST): 17 U/L Alanine aminotransferase (ALT): 14 U/L Beta-hydroxybutyrate: 0.1 mmol/L Bicarbonate: 25 mEq/L Anion

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Diabetes Mellitus, Type 1 Diabetes Mellitus, Type 2 Subject must be at least 18 years of age. 2. Subject must have a diagnosis of type 1 or type 2 diabetes mellitus. 3. Use one of the following for their diabetes management intensive insulin therapy (insulin therapy through an insulin pump and/or multiple daily insulin injections) or non-intensive insulin therapy (Basal insulin, injectable non-insulin anti-diabetic agents such as a pramlintide or GLP-1 agonists, NPH insulin either alone or in combination with regular insulin or fast acting insulin analogue, or oral medication) 4. Intensive-insulin using (IIT) subjects only During one of the in-clinic sessions, subject is willing to have their blood glucose levels manipulated into high and low glucose levels. Insulin-to-carbohydrate ratio and insulin sensitivity formula must be documented prior to having blood glucose levels manipulated. NIT subjects will only be observed during each in-clinic session. 5. For subjects that exercise routinely (at least 3 times per week), willing to exercise during at least one of the in-clinic sessions, if asked. 6. Willing to perform a minimum of 8 finger sticks per day during the study. 7. Subject must be able to read and understand English. 8. In the investigator's opinion, the subject must be able to follow the instructions provided to him/her by the study site and perform all study tasks as specified by the protocol. 9. Subject must be available to participate in all study visits. 10. Subject must be willing and able to provide written signed and dated informed consent  Subject has known allergy to medical grade adhesive or isopropyl alcohol used to disinfect skin. 2. Subject is pregnant, is attempting to conceive or is not willing and able to practice birth control during the study duration (applicable to female subjects only). 3. Subject has extensive skin changes/diseases at the proposed application sites that could interfere with device placement or the accuracy of interstitial glucose measurements. Such conditions but are not limited to extensive psoriasis, recent burns or severe sunburn, extensive eczema, extensive scarring, dermatitis herpetiformis, skin lesions, redness, infection or edema. 4. Subject is on dialysis. 5. Subject has a history of untreated hypothyroidism, adrenal gland failure or insufficiency, celiac disease, renal failure, cystic fibrosis, unstable coronary heart disease, or serious psychiatric disorders. 6. Subjects with a history of hypoglycemia unawareness, hypoglycemic seizures or unconsciousness. 7. Subjects who have experienced diabetes-related complications requiring assistance from another person in the last six months. 8. Subject currently is participating in another clinical trial. 9. Subject has donated blood within 112 days (3.7 months) prior to the beginning of the study activities. 10. Subject is anemic. 11. Subject does not have a known insulin to carbohydrate ratio at the time of enrollment (IIT subjects only). 12. Subject has concomitant medical condition which, in the opinion of the investigator, could interfere with the study or present a risk to the safety or welfare of the subject or study staff. Such conditions but are not limited to History of HIV, Hepatitis B or C 13. Subject has X-ray, MRI or CT appointment scheduled during the period of study participation, and the appointment cannot be rescheduled for a time before study participation starts or after study participation ends. 14. Subject has an abnormal EKG, unless cleared for study participation by a cardiologist. 15. Subject is unsuitable for participation due to any other cause as determined by the Investigator. Additional 16. The following subjects may participate in the study but will be excluded from all glycemic and exercise challenges Subject's taking medications known to mask symptoms or hypoglycemia, such as beta blockers Subjects with any of the following: clinically significant history of cardiovascular or cerebrovascular disease, cardiac arrhythmia, neurological disorders such as seizures, CVA, or syncope, or hypokalemia