What is idiopathic postprandial syndrome?

You frequently feel out of energy or shaky after a meal. You think you might have low blood sugar, or hypoglycemia. However, when you or your healthcare provider checks your blood sugar, it’s in the healthy range.

If this sounds familiar, you might have idiopathic postprandial syndrome (IPS). (If a condition is “idiopathic,” its cause is unknown. If a condition is “postprandial,” it occurs after a meal.)

People with IPS have the symptoms of hypoglycemia 2 to 4 hours after a meal, but they don’t have low blood glucose. This usually occurs after eating a high-carbohydrate meal.

Other names for IPS include:

  • carbohydrate intolerance
  • adrenergic postprandial syndrome
  • idiopathic reactive hypoglycemia

IPS differs from hypoglycemia in a few ways:

  • Blood sugar levels in people with hypoglycemia are below 70 milligrams per deciliter (mg/dL). People who have IPS may have blood sugar levels in the normal range, which is 70 to 120 mg/dL.
  • Hypoglycemia can lead to long-term damage of the nervous system and kidneys, but these conditions don’t happen with IPS. IPS can disrupt your daily living, but it doesn’t lead to long-term damage.
  • IPS is more common than real hypoglycemia. Most people who experience fatigue or shakiness after a meal have IPS rather than clinical hypoglycemia.

The symptoms of IPS are similar to hypoglycemia, but they’re usually less severe.

The following IPS symptoms can occur after a meal:

  • shakiness
  • nervousness
  • anxiety
  • sweating
  • chills
  • clamminess
  • irritability
  • impatience
  • confusion, including delirium
  • a rapid heart rate
  • lightheadedness
  • dizziness
  • hunger
  • nausea
  • sleepiness
  • blurred or impaired vision
  • tingling or numbness in the lips or tongue
  • headaches
  • weakness
  • fatigue
  • anger
  • stubbornness
  • sadness
  • a lack of coordination

The symptoms of IPS don’t usually progress to seizures, coma, or brain damage, but these symptoms can occur with severe hypoglycemia. Additionally, people who have hypoglycemia may not have any notable symptoms in their daily lives.

Researchers don’t know what causes IPS.

However, the following might contribute to the syndrome, especially in people who don’t have diabetes:

  • a blood glucose level that’s in the lower levels of the healthy range
  • eating foods with a high glycemic index
  • a higher blood glucose level that rapidly drops but stays within the healthy range
  • an excess production of insulin from the pancreas
  • illnesses that affect the renal system, which includes the kidneys
  • a high consumption of alcohol

Most people who have IPS don’t need medical treatment. Your healthcare provider may recommend that you modify your diet to decrease your chances of developing low blood sugar.

The following dietary changes may help:

If these dietary changes don’t provide relief, your healthcare provider might prescribe certain medications. Drugs known as alpha-glucosidase inhibitors might be particularly helpful. Healthcare providers typically use them to treat type 2 diabetes.

However, the data on efficacy, or effectiveness, of this medication in treating IPS is very sparse.

If you frequently lack energy after eating but have healthy blood sugar levels, talk with your healthcare provider about your symptoms and medical history. Working with your healthcare provider can help them identify a potential cause.

If you have IPS, making changes to your diet may help.