Insulin Overdose

What to do right away

If the person is awake and can swallow:

1. Check blood sugar if a meter is at hand, but do not delay treatment.
2. Give 15 to 20 g of fast-acting sugar: 4 glucose tablets, 4 oz (120 ml) of regular juice or non-diet soda, or a tablespoon of sugar or honey.
3. Recheck after 15 minutes. If blood sugar is still below 70 mg/dL (3.9 mmol/L) or symptoms continue, repeat.
4. Once above 70 mg/dL, eat a snack or meal with starch and protein, such as a sandwich.
5. After a real overdose, keep eating carbohydrate and checking every 1 to 2 hours, and call Poison Help or your doctor. Long-acting insulin keeps lowering blood sugar for many hours.

If the person is drowsy, unconscious or having a seizure:

1. Do not put food or drink in their mouth.
2. Give glucagon (nasal spray or injection) if available.
3. Call 911 or your local emergency number.
4. Place them on their side in the recovery position.

How an insulin overdose causes harm

Insulin moves sugar from the blood into cells and stops the liver releasing stored sugar. Too much insulin drives blood sugar down faster than the body can correct it. The brain runs almost entirely on glucose and has little reserve, so it is the organ affected first and most severely.

Insulin also pushes potassium into cells, so blood potassium can fall, raising the risk of abnormal heart rhythms.

Symptoms of an insulin overdose

Symptoms follow the level of hypoglycemia:

Some people, especially those who have had type 1 diabetes or type 2 diabetes for many years or who take beta blockers, do not feel early warning signs. During sleep, signs include nightmares, sweating through sheets, and waking with a headache or confusion.

Common causes of insulin overdose

• injecting rapid-acting (mealtime) insulin instead of long-acting (basal) insulin, or the reverse
• taking a dose twice because you forgot you had already taken it
• misreading a syringe or using the wrong concentration of insulin (for example U-500 or U-200)
• taking mealtime insulin then not eating, or vomiting after the meal
• extra exercise or alcohol without adjusting the dose
• kidney or liver disease, which slows insulin clearance
• in children, accidental injection with a family member's pen
• intentional overdose, which is associated with depression, eating disorders and suicidal thoughts, and, rarely, harm by another person

Complications

Neurological damage

The most feared complication is brain injury. Prolonged, severe hypoglycemia, especially lasting several hours with unconsciousness, can damage the cortex, hippocampus and basal ganglia. Effects range from memory and concentration problems to weakness, personality changes and, after very prolonged episodes, coma or a persistent vegetative state. Most people who are treated quickly recover fully. The risk rises with how long blood sugar stays low, not just how low it goes.

Other complications

• Seizures and injuries from falls, or road accidents if driving
• Low potassium and heart rhythm problems, including in people with heart disease
• Fluid in the lungs or brain in very large overdoses
• Rebound high blood sugar after recovery, and, in type 1 diabetes, a risk of diabetic ketoacidosis if insulin doses are then stopped altogether
• Aspiration pneumonia if the person vomits while unconscious

Hospital treatment

1. IV glucose: a bolus of concentrated glucose, then a continuous drip. Large long-acting overdoses can need glucose infusions for one to several days.
2. Frequent blood sugar checks: hourly or more often.
3. Potassium monitoring and replacement.
4. Food by mouth as soon as it is safe.
5. Heart monitoring in large overdoses.
6. Mental health assessment after any intentional overdose, before discharge.

In rare cases where a large dose was injected in one place recently, surgical removal of the tissue at the injection site has been reported, but this is not routine.

Outlook

People treated quickly for an accidental overdose usually recover completely within hours. Outcomes are worse when the overdose was large, involved long-acting insulin, was discovered late, or when the person was unconscious for a long time.

Preventing insulin overdoses

• Keep rapid- and long-acting insulin pens in clearly different places, and use pens with different colors.
• Use a logbook, app or "smart pen" that records the time of each dose.
• Never take insulin and then skip the meal it covers.
• Carry glucose tablets and keep in-date glucagon at home, work and school. Teach family how to use it.
• Use a continuous glucose monitor (CGM) with low alerts if you have frequent or unnoticed lows.
• Store insulin out of reach of children.
• If you are struggling with low mood or thoughts of self-harm, tell your doctor and ask about storing insulin safely.

Frequently asked questions

What are the symptoms of an insulin overdose?

Early symptoms are shaking, sweating, a racing heart, hunger and anxiety. As blood sugar falls further, confusion, slurred speech, blurred vision and clumsiness appear. A severe overdose causes seizures and loss of consciousness, which need glucagon and emergency care.

What should I do if I took too much insulin?

Eat or drink 15 to 20 g of fast sugar, check your blood sugar every 15 minutes until it is above 70 mg/dL, then eat a proper meal. Keep checking every 1 to 2 hours and call Poison Help at 1-800-222-1222 (US). Call 911 if you feel confused or took a large dose of long-acting insulin.

Can an insulin overdose cause brain damage?

Yes, if blood sugar stays very low for a long time. Prolonged severe hypoglycemia can injure the brain and cause memory problems, weakness or personality change. Rapid treatment usually prevents this, which is why unconsciousness or a seizure always needs emergency care.

How long does an insulin overdose last?

It depends on the insulin type and amount. Rapid-acting insulin can lower blood sugar for 3 to 5 hours. Long-acting insulin can cause lows for 24 hours or more, and large overdoses sometimes need glucose infusions for several days.

What are the long-term complications of insulin overdose?

Most people recover fully. Possible long-term effects after a severe, prolonged episode include memory and thinking problems, movement or coordination difficulty and, rarely, permanent brain injury. Repeated severe lows also blunt warning symptoms, making future episodes more dangerous.