Diabetes frequently causes nausea, which is an important indicator that the body’s glucose control is compromised or that a complication has begun to develop. This symptom signals a significant shift in internal metabolic balance that requires attention. Understanding the underlying mechanisms is the first step toward managing it effectively. The cause of the nausea can range from an acute, dangerous metabolic crisis to a chronic digestive issue resulting from long-term blood sugar fluctuations.
High Blood Sugar and Ketones
One of the most concerning causes of diabetes-related nausea involves dangerously high blood sugar, a state known as severe hyperglycemia. When there is insufficient insulin to move glucose into the body’s cells for energy, the body shifts its fuel source to stored fat. This process of fat breakdown produces acidic byproducts called ketones, which accumulate in the bloodstream and urine.
The buildup of these ketones leads to a serious medical condition known as diabetic ketoacidosis (DKA), where the blood becomes too acidic. These high levels of acidic ketones directly trigger the brain’s nausea and vomiting centers. This nausea is often accompanied by abdominal pain, excessive thirst, and frequent urination as the body attempts to flush out the excess glucose and acids.
DKA is a life-threatening emergency that develops relatively quickly, often over a 24-hour period. The presence of ketones is what distinguishes DKA from other types of severe hyperglycemia, and the resulting change in blood chemistry is the direct cause of the acute nausea. If a person with diabetes has a blood sugar reading above 250 mg/dL and begins to feel nauseous, checking for ketones is a necessary step to assess the immediate risk of DKA.
Gastroparesis
A chronic cause of persistent nausea is diabetic gastroparesis, a condition involving delayed stomach emptying. This complication is a type of diabetic neuropathy, or nerve damage, resulting from years of poorly managed blood sugar levels. Chronic hyperglycemia damages the vagus nerve, which controls the involuntary muscle contractions of the stomach.
When the vagus nerve is damaged, the stomach muscles lose their ability to contract properly and efficiently move food into the small intestine. The food lingers in the stomach for an extended period, leading to prolonged fullness and nausea, which may be accompanied by bloating. Individuals with gastroparesis often experience vomiting undigested food that was consumed hours earlier.
The delayed digestion makes blood sugar control extremely difficult because the timing of glucose absorption becomes unpredictable. A person may take their insulin to cover a meal, but the carbohydrate absorption may be delayed, leading to a period of low blood sugar followed by a spike when the food finally empties from the stomach. Gastroparesis often develops in people who have had diabetes for a decade or more.
When Nausea Requires Medical Attention
While mild, transient nausea can sometimes be managed at home, certain symptoms require immediate medical evaluation, as they may indicate the onset of DKA. A person should seek urgent care if nausea progresses to uncontrolled or persistent vomiting, especially if they are unable to keep down any fluids for several hours. This rapid fluid loss significantly increases the risk of dangerous dehydration, which worsens the underlying metabolic crisis.
Warning signs that accompany nausea and suggest a medical emergency include deep, rapid breathing, often referred to as Kussmaul respiration, or a breath odor that smells sweet or fruity. Other serious symptoms are severe abdominal pain, confusion, or unusual drowsiness. If possible, a person should check their blood sugar and ketone levels when feeling sick. A blood ketone level greater than 1.5 mmol/L, particularly with high blood sugar and vomiting, is a strong signal to go to the emergency room immediately.