Risks & emergencies

Low blood sugar (hypoglycemia)

Below 70 mg/dl (3.9 mmol/L), blood sugar counts as low — hypoglycemia. Below 54 mg/dl (3.0 mmol/L) it is severely low, and acting fast matters more than understanding why. This page covers both: what to do right now, and what low readings mean.

The 15-15 rule: treat first, investigate later

The standard first aid for a low reading in a conscious person who can swallow:

1. Take 15 grams of fast-acting carbohydrate. That is 3–4 glucose tablets, half a cup (120 ml) of fruit juice or regular soda (not diet), or a tablespoon of honey or sugar.
2. Wait 15 minutes. Resist the urge to keep eating — over-treating swings you high afterwards.
3. Re-test. Still below 70? Repeat the 15 grams. Once you are back above 70, eat a small snack with protein (crackers with cheese, half a sandwich) if the next meal is more than an hour away.

Chocolate, cookies and anything with fat work too slowly — fat delays the sugar. Fast and plain beats tasty here.

Symptoms: how low blood sugar announces itself

Early warning signs are the body releasing adrenaline: shakiness, sweating, a racing heart, sudden hunger, irritability. As glucose falls further, the brain itself runs short: confusion, slurred speech, blurred vision, clumsiness — at this stage it can look like drunkenness. Severe lows end in drowsiness, seizures or unconsciousness.

Some people who have frequent lows stop getting the early warnings (hypoglycemia unawareness). If that sounds like you, tell your care team — it changes how tightly your targets should be set.

Who gets low blood sugar?

• People on insulin or sulfonylureas. By far the most common cause: the dose, the meal and the activity did not line up. Every episode is worth logging (the journal here works for that) and discussing at the next appointment.
• People without diabetes. True hypoglycemia is uncommon. Reactive dips a few hours after a large, refined-carb meal happen; readings below 54, fainting, or lows that keep recurring deserve a medical work-up (possible causes range from medication effects to hormonal and, rarely, tumor-related ones).
• After drinking alcohol — especially on an empty stomach — the liver prioritises clearing alcohol over releasing glucose, and lows can hit hours later, including overnight.

What a single low reading means

A one-off 65 mg/dl in a healthy person who feels fine — measured on a home meter, perhaps with unwashed hands — is usually noise: home meters are allowed a ±15 % error, and a trace of anything sweet on a fingertip skews readings badly. Wash your hands, re-test. A pattern of low readings, or any low reading with symptoms, is a doctor conversation.

Preventing the next one

• Do not skip meals after taking mealtime insulin or a sulfonylurea.
• Check before driving. Below 90 mg/dl, eat first — a low behind the wheel is as dangerous as alcohol.
• Exercise pulls glucose down for up to 24 hours; long or intense sessions may need a snack or a dose adjustment (ask your care team, do not improvise).
• Keep fast sugar within reach: nightstand, car, gym bag, desk.