Insulin is a hormone produced by the pancreas that acts as a regulator, managing the amount of glucose, or sugar, circulating in the bloodstream. People with diabetes use injected insulin to replace or supplement this natural function, maintaining their blood sugar within a healthy range. While nausea is a common complaint among those managing diabetes, it is rarely due to the insulin itself. The feeling of sickness is often a signal of an underlying complication in blood sugar control or a side effect of a different, co-administered medication. Determining the exact source of nausea is a necessary step in effective diabetes management and safety.
Nausea as a Direct or Attributed Side Effect
Nausea is almost never listed as a primary, common side effect of insulin itself. In extremely rare instances, patients have reported nausea and vomiting that coincided with the start of a specific insulin formulation, such as insulin glargine. This reaction is thought to be an idiosyncratic response, possibly linked to excipients like zinc or metacresol present in some long-acting insulin analogs. Such cases are uncommon, and symptoms typically resolve when the patient switches to a different type of insulin.
A far more frequent cause of nausea is the use of other injectable diabetes medications often prescribed alongside insulin, such as GLP-1 receptor agonists. Gastrointestinal side effects, including nausea, vomiting, and diarrhea, are the most prevalent complaints with these medications, affecting up to 50% to 60% of users during the initial treatment phase. These drugs work by slowing gastric emptying, which can directly cause the feeling of fullness and sickness. If you are taking insulin and a GLP-1 receptor agonist, it is highly probable that the nausea is attributable to the latter medication.
The Hypoglycemia Connection
One of the most common diabetes-related causes of nausea is hypoglycemia, defined as a blood sugar level that drops too low (generally below 70 mg/dL). When the brain senses a lack of glucose, the body initiates a “fight-or-flight” stress response. This reaction involves the rapid release of stress hormones, particularly adrenaline, to help raise blood sugar quickly.
The surge of adrenaline affects the digestive system, causing nausea, along with other symptoms like shakiness, sweating, and confusion. This nausea signals that the body is in distress due to insufficient glucose. For mild to moderate hypoglycemia, prompt intervention is necessary to prevent the condition from worsening.
Immediate self-care involves consuming 15 to 20 grams of a fast-acting carbohydrate, such as glucose tablets, juice, or regular soda. This is often called the “15-15 rule”: the individual consumes the carbohydrate and then rechecks their blood sugar after 15 minutes. If the level remains low, the process is repeated, as treating the low blood sugar resolves the accompanying nausea.
The Hyperglycemia Connection
Nausea can also be a significant warning sign when blood sugar levels are dangerously high, a state known as hyperglycemia. This occurs when the body lacks enough insulin to move glucose into the cells for energy, forcing it to burn fat instead. This process creates acidic byproducts called ketones.
When ketones accumulate in the bloodstream, they lead to a life-threatening complication called Diabetic Ketoacidosis (DKA). Nausea and vomiting are hallmark symptoms of DKA, caused by the metabolic acidosis resulting from the ketone buildup. The presence of acetone, a type of ketone, can also cause a characteristic fruity odor on the breath.
For people with Type 1 or insulin-dependent Type 2 diabetes, nausea alongside high blood sugar (typically above 250 mg/dL) must be taken seriously. This signals that the patient’s insulin dose is insufficient or that an illness, such as an infection, is causing severe insulin resistance. The nausea is a direct result of the body’s attempt to compensate for the toxic level of acids in the blood.
When Nausea Signals a Medical Emergency
Persistent vomiting that prevents a person from keeping down fluids, food, or medication can quickly lead to severe dehydration. This inability to maintain hydration can accelerate the progression of Diabetic Ketoacidosis (DKA), making it an immediate emergency.
Other warning signs that require emergency medical care include:
- Confusion.
- Difficulty breathing, or a rapid, deep breathing pattern known as Kussmaul respirations.
- Abdominal pain or a high fever.
- Inability to reduce blood sugar levels despite taking corrective insulin doses.
- Moderate-to-large amounts of ketones present in the urine.
If you experience any of these signs or altered consciousness, seek emergency medical treatment without delay.