Insulin is a hormone that regulates the amount of glucose (sugar) circulating in the bloodstream. It works by signaling cells throughout the body to absorb glucose and use it for energy or storage. An insulin overdose occurs when a person administers more of the hormone than the body requires, resulting in a dangerously low blood sugar level, a condition known as hypoglycemia. This imbalance creates a life-threatening medical emergency requiring immediate action.
The Physiological Mechanism of Insulin Overdose
The danger of an insulin overdose stems from its potent glucose-lowering action. Excessive insulin rapidly pushes glucose out of circulation and into muscle, fat, and liver cells, significantly increasing uptake by peripheral tissues.
Excess insulin also suppresses the liver’s ability to produce glucose through glycogenolysis (breaking down stored glycogen) and gluconeogenesis (creating new glucose from non-carbohydrate sources). Both the accelerated uptake and the suppressed production cause blood glucose levels to plummet, depriving the body of its energy supply. The brain is highly dependent on a continuous supply of glucose. When this supply is cut off due to rapid hypoglycemia, neurological function quickly fails.
Recognizing Early and Moderate Symptoms
The first signs of an insulin overdose result from the body’s counter-regulatory response to falling blood sugar. As glucose levels dip, the body releases stress hormones like adrenaline, which attempt to raise blood sugar by triggering the release of stored glucose. These hormones cause noticeable physical (autonomic) symptoms that serve as early warning signals.
A person experiencing mild to moderate hypoglycemia may report feeling shaky, nervous, or anxious, often accompanied by a rapid or pounding heartbeat. Sweating and clammy skin are common, as is a sudden, intense feeling of hunger. These symptoms typically appear quickly and indicate that blood sugar is dropping below 70 mg/dL and requires immediate treatment.
As the blood sugar level continues to fall, mild cognitive changes emerge because the brain is not receiving enough fuel. The individual may become irritable, moody, or have difficulty concentrating and experience mild confusion. They may also feel dizzy, lightheaded, or experience tingling sensations around the mouth or lips. At this stage, immediate consumption of fast-acting carbohydrates, such as glucose tablets or fruit juice, is necessary to prevent the condition from worsening.
Progression to Severe Hypoglycemic Crisis
If early symptoms are not recognized or treated promptly, the condition progresses into a severe hypoglycemic crisis, often termed insulin shock. As blood glucose drops below the threshold of 54 mg/dL, the brain’s energy deprivation, known as neuroglycopenia, becomes severe. The initial signs of mild confusion give way to profound neurological dysfunction.
The person may exhibit slurred speech, blurred or double vision, and severe disorientation. They may struggle to follow simple commands or become aggressive and uncooperative, making self-treatment impossible. This severe stage is characterized by a loss of motor coordination, leading to clumsiness or an inability to walk steadily.
The crisis escalates rapidly, culminating in seizures (uncontrolled electrical disturbances in the brain). If the glucose level remains critically low, the patient will lose consciousness and enter a hypoglycemic coma. Prolonged or recurrent episodes of severe neuroglycopenia carry a risk of permanent brain damage and, without immediate medical intervention, can result in death.
Emergency Medical Intervention
Once a person is unconscious or experiencing severe neurological symptoms like seizures, the situation requires immediate professional medical intervention. The first step for anyone assisting an unconscious person is to call emergency medical services immediately. If a Glucagon Emergency Kit is available, a bystander can administer the injection, a hormone that signals the liver to release its stored glucose.
Upon arrival, the medical team administers intravenous (IV) dextrose, a concentrated glucose solution. A bolus of 50% dextrose is typically given to rapidly raise blood sugar, followed by a continuous infusion of a lower concentration, such as 10% dextrose, to maintain stability. This continuous infusion is important in cases involving an overdose of long-acting insulin, where the hormone’s effects can persist for 48 to 96 hours or longer.
The patient requires continuous monitoring of blood glucose levels, often every 15 to 60 minutes, to ensure stability. Close attention is also paid to electrolyte levels, particularly potassium, as insulin drives potassium into the cells along with glucose, which can lead to dangerously low potassium levels (hypokalemia). A prolonged hospital stay may be necessary to outlast the duration of the excessive insulin and prevent subsequent dips in blood sugar.