Hypoglycemia (Low Blood Sugar)

Overview

Hypoglycemia means blood sugar (glucose) has fallen below the normal range. Glucose is the body's main fuel, and the brain in particular depends on a steady supply, so when levels drop too low the body sounds an alarm. Early symptoms such as shakiness, sweating, hunger, and a racing heart are the body's way of prompting you to eat. If blood sugar keeps falling, the brain is affected, causing confusion, slurred speech, and, in severe cases, seizures or loss of consciousness.

Hypoglycemia is most common in people who take insulin or certain other medications for diabetes, but it can also occur for other reasons. Most episodes are mild and respond quickly to eating or drinking something sugary. Severe hypoglycemia, however, is a medical emergency. Recognizing the early signs and treating them fast is the key to staying safe.

Common Causes

Low blood sugar can have several causes:

• Diabetes medications: Insulin and some pills (such as sulfonylureas) can lower blood sugar too much, especially with too high a dose, a missed meal, or extra exercise.
• Skipping or delaying meals: Going too long without eating, particularly while on glucose-lowering treatment.
• Heavy exercise: Intense or prolonged activity uses up glucose.
• Alcohol: Drinking, especially on an empty stomach, can block the liver from releasing glucose.
• Other medical conditions: Less commonly, hormone deficiencies, certain tumors, severe liver or kidney disease, or after some weight-loss surgeries.
• Reactive hypoglycemia: A drop in blood sugar a few hours after eating in some people without diabetes.

Associated Symptoms

Symptoms tend to progress as blood sugar falls further. Early warning signs include:

• Shakiness or trembling
• Sweating and clammy skin
• Sudden hunger
• A fast or pounding heartbeat
• Anxiety, irritability, or nervousness
• Tingling around the mouth

If untreated, more serious symptoms can follow:

• Confusion or difficulty concentrating
• Slurred speech and blurred vision
• Weakness, dizziness, or poor coordination
• Seizures and loss of consciousness in severe cases

Some people, especially with long-standing diabetes, lose their early warning signs, which makes regular monitoring especially important.

Diagnosis & Evaluation

Hypoglycemia is confirmed by measuring blood sugar during symptoms and seeing it rise with treatment. Evaluation may include:

• Blood glucose testing: A finger-stick or laboratory measurement showing a low level when symptoms occur.
• Continuous glucose monitoring: A wearable sensor that tracks glucose trends, useful for people with diabetes who have frequent lows.
• Review of medications and routine: To identify triggers such as dosing, meals, alcohol, and exercise.
• Further testing: In people without diabetes, additional blood and hormone tests, and sometimes a supervised fasting study, to find the underlying cause.

Treatment & Management

Treating a low quickly is essential. For a conscious person able to swallow, follow the 15-15 rule:

• Take 15 grams of fast-acting sugar: Such as glucose tablets, half a cup of juice or regular soda, or a tablespoon of honey or sugar.
• Wait 15 minutes, then recheck: If still low, repeat the sugar. Once recovered, eat a snack or meal if the next one is more than an hour away.

For severe hypoglycemia where the person cannot safely swallow or is unconscious:

• Do not give food or drink by mouth because of the choking risk.
• Give glucagon (an injection or nasal spray) if available and you are trained, and call emergency services immediately.

Preventing future lows involves adjusting diabetes medication, meal timing, and activity with a clinician.

Self-Care & Prevention

• Eat regular meals and snacks, especially if you take glucose-lowering medication
• Check blood sugar as advised, particularly before driving and exercise
• Carry a fast-acting sugar source with you at all times
• Avoid drinking alcohol on an empty stomach
• Learn and share your early warning signs with family, friends, or coworkers
• Keep a glucagon kit if you are at risk of severe lows, and make sure others know how to use it

When to See a Doctor

See a doctor if you have repeated low blood sugar episodes, lows you cannot explain, or if you are losing your early warning signs. Call emergency services right away if someone with low blood sugar:

• Becomes confused, disoriented, or unable to follow instructions
• Has a seizure
• Loses consciousness or cannot safely swallow
• Does not improve after repeated treatment with sugar

Severe hypoglycemia is a medical emergency. Give glucagon if available and trained, place an unconscious person on their side, and do not put food or drink in their mouth.

Related Topics

Frequently Asked Questions

References

1. American Diabetes Association. Hypoglycemia (Low Blood Glucose).
2. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Low Blood Glucose (Hypoglycemia).
3. Mayo Clinic. Hypoglycemia — Symptoms and causes.
4. MedlinePlus, U.S. National Library of Medicine. Low blood sugar.