This study is designed to evaluate individuals who are currently experiencing symptoms of hypoglycemia, in order to discern correlations between microbiome composition and patterns of postprandial glycemia.

Recent studies have shown that analysis of the gastrointestinal microbiome can be used to predict glycemic response to dietary intake. Specifically, integrative analysis of dietary consumption, anthropometrics, physical activity and gut microbiota composition can be used to predict postprandial glycemic excursions. The investigators hypothesize that individualized assessment of glycemic responses to food, together with analysis of the gut microbiome, will allow the design of a personalized dietary approach to minimize glycemic excursions for patients with post-bariatric and other forms of largely postprandial hypoglycemia. Identification of factors predictive of glycemic excursions and subsequent hypoglycemia may ultimately allow individuals to tailor their diet towards foods which would not induce hypersecretion of insulin and subsequent hypoglycemia.

Inclusion Criteria

1. Males or females diagnosed with ongoing post-bariatric, post-gastric surgery or other forms of postprandial hypoglycemia with prior episodes of neuroglycopenia
2. Age 18-65 years of age, inclusive, at screening.
3. Willingness to provide informed consent and follow all study procedures, including attending all scheduled visits.

Exclusion Criteria

1. Documented hypoglycemia occurring in the fasting state (> 12 hours fast);
2. Chronic kidney disease stage 4 or 5 (including end-stage renal disease);
3. Hepatic disease, including serum alanine aminotransferase (ALT) or aspartate aminotransferase (AST) greater than or equal to 3 times the upper limit of normal; hepatic synthetic insufficiency as defined as serum albumin < 3.0 g/dL; or serum bilirubin > 2.0;
4. Congestive heart failure, New York Heart Association (NYHA) class II, III or IV;
5. History of myocardial infarction, unstable angina or revascularization within the past 6 months or 2 or more risk factors for coronary artery disease including diabetes, uncontrolled hypertension, uncontrolled hyperlipidemia, and active tobacco use.
6. History of syncope (unrelated to hypoglycemia) or diagnosed cardiac arrhythmia
7. Concurrent administration of β-blocker therapy;
8. History of a cerebrovascular accident;
9. Seizure disorder (other than with suspect or documented hypoglycemia);
10. Active treatment with any diabetes medications except for acarbose;
11. Active treatment with octreotide or diazoxide;
12. Active malignancy, except basal cell or squamous cell skin cancers;
13. Personal or family history of pheochromocytoma or disorder with increased risk of pheochromocytoma (MEN 2, neurofibromatosis, or Von Hippel-Lindau disease);
14. Known insulinoma;
15. Major surgical operation within 30 days prior to screening;
16. Hematocrit < 33%;
17. Bleeding disorder, treatment with warfarin, or platelet count <50,000;
18. Blood donation (1 pint of whole blood) within the past 2 months;
19. Active alcohol abuse or substance abuse;
20. Current administration of oral or parenteral corticosteroids;
21. Pregnancy and/ or lactation: For women of childbearing potential: there is a requirement for a negative urine pregnancy test and for agreement to use contraception during the study and for at least 1 month after participating in the study. Acceptable contraception includes birth control pill / patch / vaginal ring, Depo-Provera, Norplant, an intrauterine device (IUD), the double barrier method (the woman uses a diaphragm and spermicide and the man uses a condom), or abstinence.
22. Use of an investigational drug within 30 days prior to screening.

Patients who experience hypoglycemia after bariatric or other upper gastrointestinal surgery or those with reactive hypoglycemia in the absence of surgery.