Condition5 min read
Hypoglycaemia (low blood glucose)
hypo
Blood glucose falls below a safe level, causing shakiness, hunger, sweating and confusion. Mild episodes are treated with fast-acting sugar; a severe episode with loss of consciousness is an emergency.
In people with diabetes hypoglycaemia is usually when sugar falls below 4 mmol/L according to the NHS, or below 70 mg/dL for many according to the NIDDK. Its most common causes are insulin or some diabetes medicines, skipped meals, exertion without carbohydrates, and alcohol without food.
The NIDDK distinguishes between mild-to-moderate and severe symptoms and describes the “15-15 rule”. In severe cases (loss of consciousness or convulsion) glucagon is the recommended treatment, and no food or drink is given to someone who has lost consciousness. Having “hypoglycaemia unawareness” is a complication that requires reviewing the plan.
In one minute12
- What is it?
- Blood sugar falling below the safe level, usually below 4 mmol/L according to the NHS.
- Who is usually affected?
- Most common in people with diabetes who use insulin or some diabetes medicines.
- Acute or chronic?
- Acute episodes that can be treated quickly, and may recur.
- Main symptoms
- Shakiness, hunger, sweating, dizziness, confusion and palpitations.
- Red flags?
- Yes: loss of consciousness, convulsion or inability to swallow.
- Preventable?
- Follow the treatment plan, measure sugar, carry fast-acting sugar, and do not skip meals.
What is it?
Hypoglycaemia (“hypo”) is usually when blood sugar falls below 4 mmol/L according to the NHS, and below 70 mg/dL in many people with diabetes according to the NIDDK, and the threshold may differ from person to person.
Causes
In people with diabetes: too much insulin or an injection technique error, skipped meals, physical exertion without extra carbohydrates, alcohol without food, or an illness that reduces eating. The NIDDK lists diabetes medicines of the sulfonylurea and meglitinide classes.
In people without diabetes: rare, and its causes include malnutrition, Addison disease and pancreatic tumours.
Symptoms
Hunger, dizziness, anxiety, sweating, shakiness, tingling in the lips, palpitations, tiredness, blurred vision and confusion. It may progress to convulsion or loss of consciousness. During sleep: nightmares, excessive sweating, and confusion or irritability on waking.
Treatment
The treatment categories usually used are listed here; this is not a prescription. The doctor chooses the plan according to each person's condition; do not change any medicine or dose without a specialist.
First aid for someone conscious: fast-acting carbohydrate (15–20 grams according to the NIDDK, for example glucose tablets, juice or a sweetened soft drink), then re-measure sugar after 10–15 minutes and repeat if it has not risen, then a snack if the next meal is far off.
In severe hypoglycaemia: no food or drink is given to someone who has lost consciousness; place them in the recovery position, give glucagon if available and the person is trained, and call the ambulance.
Complications
Hypoglycaemia unawareness: the person does not recognise the symptoms of hypoglycaemia until sugar falls dangerously low.
Prevention
Follow the diabetes treatment plan, measure sugar regularly or use a continuous sensor, always carry fast-acting sugar, have a glucagon kit and inform family and friends, do not skip meals, and measure sugar before, during and after exercise. Then coordinate medicine adjustment with the doctor.
When do you need urgent help?
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- Repeated hypoglycaemia or hypoglycaemia that does not improve with fast sugar, or frequent night-time hypoglycaemia.2
See your doctor within days
- Not feeling hypoglycaemia symptoms or a change in eating and activity patterns needs the plan adjusted with the doctor.2
Educational content only — no diagnosis, and no substitute for a clinician.
Common questions
Questions for your doctor
- What hypoglycaemia threshold and sugar target suit me?
- Do I need glucagon and who should be trained to use it?
- Does any of my medicines raise the risk of hypoglycaemia?
- How do I adjust medicines and food with exercise and fasting?
- Would a continuous sensor with an alarm suit me?
References
- 1NHS. Low blood sugar (hypoglycaemia). www.nhs.uk/conditions/low-blood-sugar-hypoglycaemia/Health agencies & guidelines · Accessed 2026-10-03
- 2NIDDK / NIH. Low blood glucose (hypoglycemia). www.niddk.nih.gov/health-information/diabetes/overview/preventing-problems/low-blood-glucose-hypoglycemiaHealth agencies & guidelines · Accessed 2026-10-05
Review status: Edited content · Last updated:
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Educational content only — no diagnosis, and no substitute for a clinician.