The goal of this clinical trial is to learn if continuous glucose monitoring works to treat postprandial hypoglycaemia in patients who have undergone gastric bypass surgery. The main question it aims to answer is:

• Is continuous glucose monitoring superior to usual care for prevention of postprandial hypoglycaemia in patients with verified postprandial hypoglycaemia after gastric bypass surgery?

Researchers will compare continuous glucose monitoring to usual care to see if continuous glucose monitoring works to treat postprandial hypoglycaemia.

Participants will:

• Use a continuous glucose monitor for 6 weeks or use no continuous glucose monitor for 5 weeks and wear a blinded continuous glucose monitor for 1 week.
• Visit the clinic 2-3 times and have 2-3 phone consultations.
• Register symptoms of hypoglycaemia, answer questionnaires, undergo a 24-hour dietary recall interview conducted by a registered dietitian, measure weight and body composition and take blood samples.

Inclusion Criteria:

• Gastric bypass surgery at least 1 year ago
• Age ≥18 years
• Symptomatic postprandial hypoglycaemia; capillary glucose level <3.0 mmol/L 1-4 hours after meals

Exclusion Criteria:

• Not able to give informed consent
• Reduced compliance due to severe mental and psychiatric conditions
• Use of insulin or sulfonylureas
• Use of systemic corticosteroids
• Primary or secondary adrenal insufficiency
• Insulinoma
• Severe heart-, lung, liver- or kidney disease, cancer, malnutrition and other medical conditions causing fragility
• Performed bariatric revisional surgery
• Drug- or alcohol abuse
• Pregnancy
• Use of acarbose or octreotide in the treatment of postprandial hypoglycemia
• Use of continuous glucose monitor