Symptoms and diagnosis
Symptoms of postprandial hypoglycaemia tend to be mild to moderate. Rapid and severe symptom onset is relatively uncommon. More severe neurological symptoms of hypoglycaemia, such as loss of consciousness and seizures, can be mistaken for epilepsy.
The level of glucose at which hypoglycaemic symptoms occur varies, and different thresholds have been used for diagnosis. By definition, hypoglycaemia is not present when blood glucose is ≥ 4.0 mmol/L in a normal population (1, 2, 5). A drop in glucose initially triggers autonomic symptoms via the central nervous system, including trembling, cold sweats, dizziness and palpitations. Glucose levels below 3.0 mmol/L can trigger neuroglycopenic symptoms, such as concentration problems, memory loss, irritability, lethargy, altered consciousness and more serious clinical outcomes such as arrhythmias, seizures and coma. To meet the diagnostic criteria for hypoglycaemia, three signs must be present: low plasma glucose concentration, symptoms of hypoglycaemia and resolution of these symptoms when plasma glucose concentration is normalised (Whipple's triad) (1, 5, 8).
The symptom profile of postprandial hypoglycaemia resembles the hypoglycaemic symptoms seen in diabetes mellitus. A medical history of diabetes or previous bariatric surgery therefore provides important information about the underlying cause. In diabetes, hypoglycaemia is typically associated with the use of insulin or other antidiabetic medications.
A characteristic feature of post-bariatric hypoglycaemia is meal-related fluctuations and imbalances in glucose and insulin levels, as well as the time it takes for postprandial symptoms to appear (5, 8). Plasma glucose concentration often rises excessively within the first 30 minutes, triggering a supraphysiological insulin response. It subsequently drops, potentially low enough to cause hypoglycaemic symptoms, typically 1–3 hours after a meal. Symptoms often emerge 1–3 years after surgery. Fasting blood glucose levels are usually normal. Hypoglycaemic episodes have also been observed independently of meals, including during fasting or at night.
Symptoms of early dumping occur sooner after eating and are often also triggered by carbohydrates, but they may also be caused by high-fat foods or by eating too much or too quickly. The symptom profile typically includes vasomotor and gastrointestinal symptoms such as a warm sensation, palpitations, nausea, diarrhoea and abdominal pain (9).
In acute cases and recurrent episodes, capillary blood glucose self-monitoring is recommended, along with recording symptoms and prior food intake (3). Table 1 shows suggested glucose thresholds, clinical interpretations and interventions. Raising awareness about diet is essential, and follow-up with a clinical nutritionist may be necessary. In the specialist health service, a meal challenge provocation test is preferred for diagnosis over an oral glucose tolerance test (3, 5). Continuous glucose monitoring in interstitial fluid is sometimes used, but this method has limitations due to time lags and reduced accuracy at low glucose levels.
Table 1
Blood glucose levels for hypoglycaemic symptoms after bariatric surgery, and suggested clinical interpretations and interventions
| Blood glucose (mmol/L) | Interpretation | Relevant intervention |
|---|
| ≥ 4.0 | Hypoglycaemia unlikely | Capillary measurement during symptoms |
| 3.0–3.9 | Suspected hypoglycaemia if symptoms are present | General dietary advice |
| < 3.0 | Hypoglycaemia likely | Targeted dietary advice
Refer to specialist if symptoms are significant |
| < 2.0 | Likely and severe | Glucose administration during episodes
Refer to specialist |