The body relies on a constant, tightly regulated supply of glucose, or blood sugar, which acts as its primary fuel source necessary for every cell and organ to function. When this fuel supply malfunctions—either too high or too low—the body sends distress signals. A common consequence of these fluctuations is the onset of nausea.
Nausea Triggered by High Blood Sugar
When glucose levels remain excessively high (hyperglycemia), the body can experience serious physiological reactions that lead to severe nausea. The most acute danger is diabetic ketoacidosis (DKA), which occurs when the body lacks sufficient insulin to move glucose into cells for energy. Without glucose, the body breaks down fat stores, producing acidic byproducts called ketones. High concentrations of these ketones build up in the bloodstream, raising the blood’s acidity, which directly triggers the brain’s vomiting center.
The resulting nausea and vomiting are often accompanied by extreme thirst, frequent urination, and a distinctive fruity odor on the breath from excess ketones. This severe, acute nausea signals a dangerous medical emergency requiring immediate treatment with intravenous fluids and insulin.
Diabetic Gastroparesis
A different, more chronic cause of nausea linked to high blood sugar is diabetic gastroparesis. This condition involves damage to the vagus nerve, which regulates the movement of food through the digestive tract. Years of poorly controlled high blood sugar can cause chemical changes that harm this nerve over time.
When the vagus nerve is damaged, the stomach muscles do not contract properly, causing delayed gastric emptying. This leads to chronic symptoms like bloating, feeling full quickly, and persistent nausea. Undigested food can sometimes harden into a mass called a bezoar, which further aggravates the stomach lining. Even an acute spike in blood sugar can temporarily slow down gastric emptying, causing short-term nausea.
Nausea Triggered by Low Blood Sugar
Nausea can also be a symptom of hypoglycemia, defined as blood sugar levels that are too low (typically below 70 mg/dL). This rapid drop in energy prompts an immediate “fight-or-flight” response. To quickly raise glucose levels, the body floods the system with stress hormones, most notably adrenaline.
The sudden surge of adrenaline mobilizes glucose reserves and produces immediate systemic effects, including a rapid heartbeat, sweating, paleness, and shakiness. Adrenaline is a powerful hormone, and its sudden release can irritate the digestive tract, directly leading to feelings of nausea.
This nausea is often felt alongside other symptoms of the adrenaline rush, such as internal trembling. The nausea generally resolves quickly after consuming fast-acting carbohydrates that restore glucose to a safe range.
Emergency Signs and Medical Intervention
Recognizing the cause of blood sugar-related nausea requires immediate action, starting with checking the current glucose level. If the reading is extremely low, immediate consumption of 15 grams of fast-acting carbohydrates, such as glucose tablets or fruit juice, is the appropriate self-treatment. Nausea related to low blood sugar should improve significantly within 15 to 20 minutes.
If the blood sugar reading is very high (often above 250 mg/dL) and accompanied by severe nausea, vomiting, or abdominal pain, it may indicate ketoacidosis. In this scenario, checking for ketones using a urine or blood test is important. The inability to keep down fluids can worsen the underlying metabolic problem and lead to dangerous dehydration.
Any persistent vomiting that prevents a person from keeping down fluids warrants immediate medical attention, regardless of the blood sugar level. Other emergency signs include confusion, difficulty breathing, or any loss of consciousness. These symptoms signal a life-threatening complication requiring professional intervention to correct the body’s chemical imbalance.