Insulin is a naturally occurring hormone responsible for regulating the amount of glucose in the bloodstream. It acts by signaling cells throughout the body to absorb glucose from circulation, utilizing it for energy or storing it for later use. This process maintains blood sugar levels within a healthy range. When a person injects more insulin than the body needs, the resulting imbalance triggers a sharp drop in blood glucose, a condition known as hypoglycemia. This state of low blood sugar is the most serious consequence of an insulin overdose, requiring immediate recognition and treatment to prevent severe complications.
How Excess Insulin Causes Hypoglycemia
The core function of injected insulin is to facilitate the movement of glucose out of the bloodstream and into muscle, fat, and liver cells. When an excessive dose is administered, this glucose clearing process accelerates dramatically, removing sugar from the blood faster than the body can replenish it. Since the brain relies almost exclusively on glucose for fuel, this rapid depletion quickly leads to energy deprivation in the central nervous system.
The body attempts to counteract this sudden drop by releasing counter-regulatory hormones, primarily glucagon, from the pancreas. Glucagon signals the liver to release its stored glucose (glycogen) into the bloodstream to raise the failing blood sugar level. However, in the case of an overdose, the excess insulin overwhelms the body’s natural defense mechanisms, causing them to fail.
The duration of the overdose effect depends heavily on the type of insulin taken. A rapid-acting or bolus insulin overdose causes a quick, intense drop in blood sugar that may last for a few hours. In contrast, an overdose of long-acting or basal insulin creates a less immediate but more prolonged risk of hypoglycemia, potentially affecting glucose levels for 24 hours or longer. This extended period requires sustained monitoring and treatment.
Identifying the Symptoms of Low Blood Sugar
Recognizing the signs of hypoglycemia is important, as symptoms begin quickly and can vary widely between individuals. Mild or early symptoms often manifest from the body’s release of stress hormones in response to low glucose. These early warning signs include feeling shaky or jittery, breaking out in a cold sweat, and experiencing a rapid heartbeat. Other initial symptoms are sudden hunger, nervousness, anxiety, or a tingling sensation in the lips, tongue, or cheeks.
As the blood glucose level continues to fall below a threshold of about 55 milligrams per deciliter, the brain begins to show effects of glucose deprivation. Moderate symptoms of hypoglycemia reflect this loss of normal brain function, often presenting as confusion, difficulty concentrating, or slurred speech. A person may also exhibit mood changes such as irritability, unusual weakness, or sleepiness, and they might have difficulty walking or coordinating their movements.
Severe hypoglycemia represents a medical emergency, typically occurring when blood glucose drops to very low levels. At this stage, the brain’s function is profoundly impaired, which can lead to seizures or a complete loss of consciousness, sometimes referred to as insulin shock. A person experiencing severe symptoms may be unable to swallow or help themselves, requiring immediate assistance.
Emergency Treatment and Response
The immediate treatment for hypoglycemia depends on the person’s ability to remain conscious and safely swallow. If the individual is awake and alert, the standard procedure is to consume a fast-acting source of carbohydrate, such as fruit juice, regular soda, or glucose tablets. This approach is formalized as the “Rule of 15s”: the person consumes 15 grams of fast-acting carbohydrate, waits 15 minutes, and then rechecks their blood sugar.
If the blood glucose level remains below 70 milligrams per deciliter after the initial treatment, the process is repeated until the level rises above this threshold. Once the blood sugar has stabilized, a small snack containing protein and a longer-acting carbohydrate, such as crackers or bread, should be eaten. This helps prevent a secondary drop in blood sugar, especially following a large insulin dose.
For a person who is unconscious, having a seizure, or unable to swallow, no food or liquid should be given by mouth due to the risk of choking. Treatment must shift to administering emergency glucagon, which is available as an injectable or a nasal spray. Glucagon quickly triggers the liver to release its stored glucose, rapidly raising blood sugar.
It is important to seek immediate emergency medical services if glucagon is unavailable, if the individual does not regain consciousness within 15 minutes of receiving glucagon, or if symptoms worsen. Massive insulin overdoses, especially those involving long-acting insulin, can cause prolonged and unpredictable hypoglycemia that requires professional medical intervention, often involving continuous intravenous glucose administration.
Avoiding Accidental Insulin Overdose
Preventing an accidental insulin overdose centers on strict adherence to routine and careful administration techniques. Key preventative measures include:
- Double-checking the dose dialed into the pen or drawn into the syringe before every injection to avoid misreading markings.
- Establishing a clear system for distinguishing between rapid-acting and long-acting insulin, perhaps by using color-coded labels.
- Never skipping a meal after taking a dose of mealtime insulin, as insulin is dosed to match food intake.
- Regularly tracking and logging all injections and blood sugar readings to help identify patterns or mistakes.
If a meal is delayed or missed, the insulin dose should be adjusted or the meal should be eaten immediately to avoid a mismatch between circulating insulin and available glucose. If there is any concern about the correct dosage, a healthcare provider should be consulted.