Recognising and treating a hypo
Hypoglycaemia — a hypo — means blood glucose below 70 mg/dL (3.9 mmol/L). It causes shaking, sweating, hunger, a pounding heart and confusion, and it comes on over minutes. Treat it at once with 15 grams of fast-acting sugar such as half a cup of juice, three teaspoons of sugar in water, or four glucose tablets, then re-check after 15 minutes and repeat if it is still low. Once the reading is above 70, eat something longer-lasting. Hypos are caused by insulin and sulfonylureas, not by metformin alone, and anyone who cannot swallow or has passed out needs emergency help, not food in the mouth.
Diabetologist & General Physician · MBBS
A hypo is what happens when there is more glucose-lowering medicine in the body than there is glucose for it to work on. The brain runs almost entirely on glucose and has no store of its own, which is why the symptoms are so quick and so dramatic: this is an organ that notices within minutes.
What it feels like
| Early (adrenaline) | Later (brain running short) |
|---|---|
| Shaking, trembling | Confusion, difficulty concentrating |
| Sweating, clammy skin | Slurred speech |
| Pounding or racing heart | Blurred or double vision |
| Sudden hunger | Unusual behaviour, irritability, aggression |
| Tingling around the lips | Drowsiness, then unconsciousness |
| Anxiety without reason | Fits (seizures) |
The 15-15 rule
- Take 15 grams of fast-acting carbohydrate.
- Wait 15 minutes. Do not keep eating during this time — this is the mistake that turns a hypo into a sugar of 300.
- Re-check your blood glucose.
- If still below 70 mg/dL, repeat with another 15 grams.
- Once above 70, eat a snack or meal containing slower carbohydrate and protein if your next meal is more than an hour away.
What counts as 15 grams
- 3 teaspoons of sugar dissolved in water
- Half a cup (about 120 ml) of fruit juice or regular (not diet) soft drink
- 4 commercial glucose tablets
- 1 tablespoon of honey — not for children under one year
- 3–4 pieces of hard sugar candy, chewed
If the person cannot swallow
Why it happened
Every hypo has a cause, and finding it is how the next one is prevented. Ask what was different about that day.
- A meal was delayed, skipped or smaller than usual
- The insulin or sulfonylurea dose was too high, or was taken twice by mistake
- More physical activity than usual — including housework, walking to the bazaar, or taraweeh
- Alcohol, which blocks the liver from releasing stored glucose
- Kidney function has declined, so medicines clear more slowly
- Weight loss or improved diet, meaning the old dose is now too strong
Which medicines cause hypos
| Higher risk | Low risk on their own |
|---|---|
| Insulin (all types) | Metformin |
| Sulfonylureas — gliclazide, glimepiride, glibenclamide | DPP-4 inhibitors — sitagliptin, linagliptin |
| Meglitinides — repaglinide | SGLT2 inhibitors — empagliflozin, dapagliflozin |
| GLP-1 agonists — semaglutide, liraglutide |
Hypo unawareness
Some people who have had diabetes for many years, or who have frequent hypos, stop getting the early adrenaline warnings and go straight to confusion. This is dangerous and it is reversible: deliberately keeping glucose a little higher for a few weeks, under medical supervision, often restores the warning symptoms. Tell your doctor if you no longer feel your hypos coming.
Driving
Check your glucose before driving if you take insulin or a sulfonylurea. If it is below 90 mg/dL, eat before setting off. If you have a hypo while driving, stop, take the key out of the ignition, treat it, and wait 45 minutes after your glucose is back to normal before driving on — judgement recovers more slowly than the number does.
Common questions
Still not sure what to do?
Reading about a symptom only goes so far. A doctor who can ask you questions and examine you will get further in ten minutes than any article can.
