Many of us have experienced a “food coma” — a peaceful feeling of sleepiness after eating a carb-heavy meal. For some, it’s practically a holiday tradition.

But this idea of post-meal sleepiness takes on an entirely different meaning for people with diabetes. Feeling sleepy after eating may be a sign of high or low blood sugar. In extreme cases, blood sugar that’s too high or too low can cause someone to feel so weak that they lose consciousness. This is known as a diabetic coma, and it’s life threatening.

You might think you’re protected from diabetic fatigue if you take insulin shots or other diabetes medications. However, your body needs different amounts of insulin based on what, how much, and how often you eat. Too much insulin can cause your blood sugar levels to drop too low, while too little insulin can cause them to spike. Fatigue after a meal could be one of the signs that your insulin dosage needs to be adjusted.

That said, fatigue is a possible symptom of many other medical concerns. We’ll explain some of the potential culprits below, but you should talk to your healthcare provider to get to the bottom of your extreme tiredness.

Diabetes Fatigue Feels ‘Heavy’ and Persistent

It’s normal to feel tired at the end of a productive day, but fatigue is a different story. People with fatigue feel so tired that they often can’t complete their daily activities. They may experience an urgent need to sleep but find that sleep doesn’t restore their energy levels.

Other symptoms of fatigue include low motivation, irritability, anxiety, depression, difficulty concentrating, and muscle weakness.

DiabetesTeam members share some of their experiences with fatigue:

• “When I fall asleep for more than just a short nap, I look at what I ate. I cross that off my diet or really cut down on how much I eat.”
• “I feel very sleepy during the day, but not a healthy tired ‘sleepy,’ more like a drugged, heavy, slow feeling that doesn’t lift much.”
• “I find when I feel tired it’s because of illness, deficiencies, lack of exercise, not outdoors enough, lack of good sleep, or low blood glucose.”
• “Last night, I was so tired it hurt. I ate a slice of ham and a piece of aged cheddar. Within 15 minutes, I felt better. It appears my numbers were too low.”
• “I’m sleepy all the time. […] I’m exhausted but can’t sleep.”
• “Does anyone else feel so sleepy you sleep most of the day?”

Blood Sugar Imbalances Can Cause Sleepiness

Having too much sugar in your blood (hyperglycemia) may cause fatigue. Blood sugar levels can quickly rise after eating a meal high in simple and refined carbohydrates, like white flour, sugar, and syrup. The pancreas releases insulin to move sugar out of the bloodstream and into the body’s cells, where it can be used for energy. But people with diabetes have trouble producing or responding to insulin.

This can cause persistent high blood sugar levels and lead to classic symptoms of diabetes, such as drowsiness, headache, and frequent urination. Dehydration, which may result from frequent urination, can also cause fatigue.

Without Insulin, the Body Burns Fat for Energy

We often associate sugar with energy, so it may seem odd that sugar can make some people feel tired. According to experts, the body stops breaking down sugar when insulin levels get low and begins breaking down fat for energy instead. This is a slower process, so it takes longer to “harvest” the energy we need in the form of a molecule called ATP. Less ATP means less energy, and less energy means more fatigue.

If the body continues to burn fat for too long, by-products called ketones build up in the bloodstream. This can cause a serious condition called diabetic ketoacidosis (DKA). If you experience DKA, fatigue may be one of several symptoms, including vomiting, stomach pain, shortness of breath, and confusion. DKA requires immediate medical attention.

Sleepiness Is Also a Sign of Low Blood Sugar

Feeling sleepy and sluggish could also mean your blood sugar levels are too low, which is known as hypoglycemia. Other symptoms of hypoglycemia include weakness, a rapid heartbeat, shakiness, anxiety, and hunger. Hypoglycemia is easily treated by eating sugar, but it is potentially fatal if left untreated.

You might experience hypoglycemia after eating if your diabetes medications work a little too well, causing more insulin to enter your bloodstream than necessary. If you eat less than usual but don’t adjust your insulin dose, the same issue can occur.

If you follow a strict ketogenic diet (which shuns most carbohydrates in favor of fat and protein), there’s also a chance you could develop hypoglycemia from a lack of sugar intake.

Prevent Post-Meal Fatigue With Lifestyle Changes

Ready to feel alert? These tips could help you have more energy after eating:

• Talk to your doctor about your insulin dose — It may need to be adjusted to avoid hyperglycemia or hypoglycemia after eating.
• Use a continuous glucose monitor — This device alerts you to blood sugar spikes and dips so you can eat something or take medication. It could help you pinpoint the foods or eating habits that often lead to post-meal sleepiness.
• Eat smaller, more frequent meals — Your body spends more energy digesting large meals, and large quantities can trigger the body to release a hormone that promotes drowsiness.
• Balance protein, carbs, and fats — You may feel more tired after eating a protein- or carb-heavy meal, so choosing well-balanced snacks and meals is key.
• Drink less caffeine — Energy slumps could also be caused by an afternoon “caffeine crash.” Lowering your caffeine intake could give you more consistent energy throughout the day and help you sleep better at night.
• Improve your nighttime sleep quality — You might be tired after a meal because you’re tired in general. Creating a relaxing routine around sleep, avoiding screens and alcohol an hour before bed, and dialing down the thermostat at night may help.
• Drink more water — Because dehydration can cause fatigue, it’s important to drink plenty of water throughout the day to keep your energy up.
• Find a way to relax — Chronic stress can be a source of fatigue in and of itself and may lead to health problems, including issues with digestion, cognition, and heart function. If you’re not sure where to start, try exercise and meditation.
• Engage in light activity after meals — Exercise supports overall health, including heart and lung function, and can help boost your energy levels. Research also shows that even a few minutes of walking after a meal can improve blood sugar control.

You Might Feel Tired for Nondiabetic Reasons

If you continue to feel excessively tired throughout the day even after getting your blood sugar under control, talk to your doctor about other potential causes.

Fatigue can be a symptom of many other health conditions, including:

• Low iron (anemia)
• An electrolyte imbalance in your blood (dyselectrolytemia)
• Low vitamin levels
• Thyroid problems (hypothyroidism or hyperthyroidism)
• Sleep apnea
• Kidney disease
• Fibromyalgia
• Depression
• Inflammatory bowel disease
• Multiple sclerosis
• Drug withdrawal

Your healthcare provider can screen you for these conditions or help you develop healthier habits to keep them at bay.

Talk With Others Who Understand

DiabetesTeam is the social network for people with diabetes and their loved ones. On DiabetesTeam, members come together to ask questions, give advice, and share their stories with others who understand life with diabetes.

Have you noticed a connection between what you eat and how tired you feel afterward? What has helped you stay alert throughout the day? Share your experience in the comments below, or start a conversation by posting on your Activities page.