Hypoglycaemia: low blood sugar and how to correct it fast

What it is, in plain words

Hypoglycaemia means blood glucose below about 3.9 mmol/L, or 70 mg/dL. The body reacts first with adrenaline, producing shaking and sweating, then, if sugar keeps falling, the brain itself runs short of fuel and thinking and consciousness are affected. Both phases are important to recognise.

Signs to look out for

• Early: shaking, sweating, palpitations, hunger, anxiety, tingling lips
• Later: difficulty concentrating, slurred speech, blurred vision, odd behaviour or aggression
• Severe: confusion, seizures, loss of consciousness
• Night-time: nightmares, sweating, morning headache and unusual tiredness
• Loss of the early warning signs after years of diabetes, called hypoglycaemia unawareness

Why it happens

Most cases occur in people treated with insulin or sulfonylureas, after too much medicine, a missed meal, unusual exercise or alcohol. Rare causes without diabetes include insulin-producing tumours, adrenal insufficiency and severe liver disease.

How doctors confirm it

Confirmation is by fingerstick or continuous glucose monitoring. In people without diabetes, investigation includes measuring insulin, C-peptide and cortisol during a documented low episode.

Treatments and solutions

• The rule of 15: take 15 g of fast sugar such as three glucose tablets, 150 ml of fruit juice or a sugary drink, wait 15 minutes, retest, and repeat if still low
• Follow with a longer-acting carbohydrate such as bread or a biscuit if the next meal is more than an hour away
• Never give anything by mouth to someone who is unconscious or fitting: use glucagon by injection or nasal spray and call emergency services
• Reviewing insulin doses, timing, exercise and alcohol habits with the diabetes team after any severe episode
• Continuous glucose monitoring with alarms, which is particularly valuable in hypoglycaemia unawareness

Living with it day to day

Carry fast sugar at all times, tell colleagues and family what to do, and be careful with driving: check glucose before setting off and do not drive below 5 mmol/L.

When to seek medical help

Seek emergency help for loss of consciousness, seizures, or repeated lows that you cannot explain or correct.

This article explains general health information in simple language. It does not replace advice from your own doctor.