Reactive hypoglycemia is a subtype of hypoglycemia characterized by a drop in blood glucose levels that occurs 2 to 5 hours after eating, and varying definitions may include dysfunctional insulin responses. It can affect both people with and without diabetes and is categorized into 3 forms based on the timing of symptoms after meals.

Reactive hypoglycemia shares symptoms with mild hypoglycemia — including heart palpitations, tremors, anxiety, and nausea — due to autonomic nervous system activation. As blood glucose levels drop further, additional symptoms such as vision disturbances, cognitive changes, and seizures may occur.

Diagnosing reactive hypoglycemia (RH) is challenging because it involves ruling out other conditions and relies on a comprehensive symptom and medical history, and no standardized tests are available. Blood glucose assessments can confirm hypoglycemia, but there is no established cutoff level for diagnosing RH, though a blood glucose level below 70 mg/dL (3.9 mmol/L) is often considered a significant indicator.

The main medical treatment for reactive hypoglycemia involves addressing any identifiable underlying medical conditions. In the absence of such conditions, lifestyle and dietary modifications, including balancing meal composition and increasing fiber intake, may help alleviate symptoms.

Currently, no supplements have been specifically studied for reactive hypoglycemia, but some that are effective for dumping syndrome (such as guar gum, pectin, and glucomannan) may also help. Additionally, traditional Chinese herbs have been explored for symptom relief, though more high-quality studies are needed to assess their efficacy and safety.

Diet significantly influences reactive hypoglycemia (RH) by affecting blood sugar levels; therefore, limiting the intake of high simple carbohydrates, refined sugars, and alcohol is a key recommendation. Additionally, meal composition, timing, and fiber content can help manage symptoms, though dietary adjustments may vary based on individual causes of RH.

Treatment for reactive hypoglycemia (RH) may include pharmaceuticals like metformin and acarbose, depending on the individual's triggers. For people with RH after gastric bypass surgery, a low-glycemic-index diet and alpha-glucosidase inhibitors are recommended, and surgical correction may be necessary if symptoms continue.

Reactive hypoglycemia is a complex condition with unclear causes and is often triggered by meals high in simple carbohydrates that lead to faulty insulin responses and subsequent low blood glucose levels. Potential contributing factors include enlarged or increased numbers of insulin-producing islet cells, anti-insulin antibodies, altered liver glucose regulation, tumors, neuropsychiatric diseases, and digestion or insulin dysfunction, particularly after gastric surgery.