Low Blood Sugar (Hypoglycemia): Symptoms and the 15-15 Rule

What counts as low

Hypoglycemia is generally defined as blood glucose below 70 mg/dL (3.9 mmol/L). Below 54 mg/dL (3.0 mmol/L) is considered clinically significant and needs immediate action.

Symptoms

• Shakiness, sweating, chills
• Fast heartbeat
• Hunger, irritability or anxiety
• Dizziness, confusion, difficulty concentrating
• Blurred vision; in severe cases seizures or loss of consciousness

The 15-15 rule

If you can check, confirm the low with a meter. Then:

• Eat or drink 15 grams of fast-acting carbohydrate — e.g. 4 glucose tablets, half a cup (120 ml) of fruit juice or regular soda, or 1 tablespoon of sugar or honey.
• Wait 15 minutes and recheck.
• If still below 70 mg/dL, repeat.
• Once normal, eat a snack or meal if your next meal is more than an hour away.

Emergencies

If someone is unconscious or cannot swallow safely, do not put food in their mouth. Use prescribed glucagon if available and call emergency services.

Prevention

Frequent lows are a signal to review your treatment with your doctor. Keep fast-acting sugar with you, be cautious with alcohol (it can cause delayed lows), and check before driving.

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