You may feel tired after eating for several reasons, including being an undiagnosed diabetic. Keep a food and activity journal to help you and your doctor identify the cause of your fatigue. Implementing dietary and other lifestyle changes may alleviate your symptoms, but before modifying your daily routine, speak with your doctor to determine if medical testing is necessary to rule out or confirm a diabetes diagnosis.
Type 1 Diabetes
Type 1 diabetes is an autoimmune disease. The body recognizes insulin-producing beta cells found in the pancreas as foreign intruders and destroys them. Without these cells, the body produces little to no insulin. Type 1 diabetics must take insulin via injections or through an insulin pump to sustain life. Without insulin, your blood glucose levels elevate after eating, causing symptoms such as fatigue, hunger, extreme thirst, frequent urination, tingling of the limbs and blurry eyesight. A healthy diet that limits sweets and other simple carbohydrates and includes lean proteins, fiber, whole grains, fruits and vegetables helps diabetics adequately control their blood glucose levels.
Type 2 Diabetes
Type 2 diabetes occurs as a result of the body's inability to correctly use or produce insulin. MedlinePlus reports that individuals with excess body fat are more likely to develop Type 2 diabetes because fat interferes with insulin use; normal-weight people can also develop this disease. Symptoms of Type 2 diabetes are similar to those of Type 1 diabetes and include fatigue, increased appetite and thirst, slow-healing infections, frequent urination, blurred vision and erectile dysfunction. A person with this condition may experience fatigue after eating when blood glucose levels are poorly controlled. If your food journal indicates that you tire after eating sugary foods or simple carbohydrates and you demonstrate other symptoms of Type 2 diabetes, visit your doctor for testing.
If your doctor suspects that diabetes is to blame for your feelings of fatigue after eating, he will order a blood test to confirm his diagnosis. He may test your fasting blood glucose levels, which must be more than 126 mg/dL on two separate testing occasions for an affirmative diagnosis. He may order an oral glucose tolerance test, which requires you to drink a designated amount of a sugary beverage depending on the duration of the test. A blood glucose level of 200 mg/dL or higher two hours after consuming the beverage indicates diabetes. A blood sample may be taken to conduct an A1C test to obtain a two- to three-month average of your blood glucose levels. A result of 6.5 percent or higher indicates poorly controlled blood glucose levels and diabetes.
Other Causes of Fatigue
If you feel fatigued after eating but have no other symptoms of diabetes and no risk factors such as family history, race or ethnicity, age or a previous diagnosis of glucose intolerance, there may be several other explanations. The brain produces chemicals called orexins when feelings of hunger develop. Orexins stimulate your nervous system, and you become alert to locate food. After eating, the brain ceases its production of this chemical, causing your awakened feeling to diminish. You may feel fatigued, but a brisk 15-minute walk will trigger your cells to uptake glucose present in the blood for energy, making your sluggish feelings subside. Reactive hypoglycemia, a condition characterized by the excessive production of insulin, which causes a sudden drop in blood glucose levels one to three hours after eating, also causes fatigue after meal consumption.