Feeling Tired After a Meal? Here's What It Might Mean

Feeling tired after eating can be perfectly normal if you've had certain foods or had a big meal.

Feeling tired after eating isn't usually a sign of diabetes — unless you also have other symptoms. Credit: Vladimir Vladimirov/E+/GettyImages

Simply feeling tired after eating isn't usually a sign of diabetes (or other medical conditions), Heidi Quinn, RDN, a certified diabetes educator at Harvard's Joslin Diabetes Center, tells LIVESTRONG.com. However, "overall fatigue" might be, she says.

As it turns out, food, fatigue and diabetes are closely linked. Here's what you need to know.

Read more: 9 Surprising Reasons You're Tired All the Time

What Exactly Is Diabetes?

Diabetes is a metabolic disorder in which the body is unable to properly use glucose (or blood sugar), the body's main source of energy, according to the Cleveland Clinic. When you eat, your body metabolizes the carbohydrates in food into glucose. The hormone insulin then helps move the glucose out of the bloodstream and into the cells.

But people with diabetes either don't produce enough insulin (type 1 diabetes) or can't use insulin effectively (type 2 diabetes). This causes glucose to build up in their blood, resulting in high blood sugar.

Elevated blood sugar levels can also be a sign of prediabetes. Prediabetes occurs when blood sugar levels are higher than normal but not high enough to be considered diabetes. If left untreated, however, prediabetes can progress into type 2 diabetes, according to the Joslin Diabetes Center.

Read more: What to Know About Normal Blood Sugar Levels in Women

The Link Between Fatigue and Diabetes

General fatigue can be a sign of untreated diabetes. "When insulin is not able to get glucose into the cells, the body doesn't get the energy it needs," Quinn says. This can cause a person to feel sleepy all the time — not just after meals.

If persistent fatigue is accompanied by other symptoms, it may be cause for concern. "If a person is drinking more, urinating more or has unexplained weight loss, they should definitely go see a doctor," Quinn says. Excess urination, thirst and unexplained weight loss are some of the most common signs of diabetes.

In rare cases, diabetes or prediabetes may cause fatigue after eating due to a condition called reactive hypoglycemia or post-meal low blood sugar, according to the Hormone Health Network. This condition can occur if the body releases too much insulin in response to food.

For example, if someone with prediabetes or diabetes eats a high-carb meal, it will typically result in high blood sugar. If the body then releases too much insulin to correct this, too much glucose can be removed from the blood. This can cause low blood sugar for up to four hours after eating, according to the Mayo Clinic.

Read more: What Really Happens to Your Body When You Drastically Cut Carbs

Other symptoms of low blood sugar include feeling hungry, shaky, dizzy, confused or irritable, according to the Hormone Health Network. If you regularly experience these symptoms after eating, see a doctor. Though rare, reactive hypoglycemia can be caused by a number of medical conditions, not just diabetes.

The takeaway: Feeling sleepy after eating isn't usually a sign of diabetes if there are no additional symptoms.

Other Causes of Sleepiness After Eating

What you eat could make you ready for a nap after a meal. Loading up on sugary foods can result in an energy crash, for example. According to the National Sleep Foundation, eating lots of sugar can reduce the activity of orexin cells, which help regulate wakefulness.

Tryptophan, found in turkey, is often cited as the cause of sleepiness after a Thanksgiving feast. Cheese, fish and other high-protein foods also contain the amino acid. Tryptophan tends to increase serotonin levels, one of the hormones involved in sleep, according to the Cleveland Clinic.

But, according to the National Sleep Foundation, tryptophan doesn't immediately make you sleepy. A more plausible cause of post-meal drowsiness? Meal size. "Tiredness after eating may just mean that a person ate too much," says Quinn.

Read more: 4 Reasons You're So Tired After a Workout and What to Do About It

When to See a Doctor

If you feel sleepy all the time and are also experiencing excess urination, excess thirst, headaches or unexplained weight loss, see a doctor. She or he will likely prescribe an oral glucose tolerance test, which is used to test for diabetes. If you receive a diabetes diagnosis, the good news is that this condition can be very manageable through lifestyle changes and medication.

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