Low blood sugar (hypoglycemia): symptoms, causes and safety

Low blood sugar, called hypoglycemia, can come on quickly and may be frightening if you have never had it. Knowing the signs helps you and the people around you act early. This article explains what the health agencies say about symptoms, causes and prevention. It is general education, not a personal plan.

What is low blood sugar?

The NIDDK describes low blood glucose as a level that drops below what is healthy for you. For many people with diabetes this means a reading below 70 mg/dL, but your care team can tell you what level counts as low for you. The NHS says low blood sugar is usually when glucose falls below 4 mmol/L, and that it is usually treatable at home but needs quick action.

Common symptoms

The NIDDK lists mild to moderate symptoms such as shakiness, hunger, tiredness, dizziness, confusion, irritability, a fast or irregular heartbeat, headache and trouble seeing or speaking clearly. The NHS adds sweating, anxiety, tingling lips and palpitations. During sleep, the NIDDK says low blood sugar may cause crying out, nightmares, damp sheets from sweating, or feeling tired, irritable or confused on waking. Some people have no symptoms at all.

Severe low blood sugar can stop the brain working properly. The NIDDK says it can lead to passing out or a seizure and needs immediate treatment.

Why does it happen?

In people with diabetes, the NIDDK lists these causes:

• Insulin, or other medicines that prompt the pancreas to release insulin
• Not eating enough carbohydrates, or skipping or delaying meals
• Fasting while still taking glucose-lowering medicines
• Extra physical activity, which can lower glucose for up to 24 hours
• Drinking alcohol without enough food
• Illness that reduces eating or keeping food down

The NHS notes that low blood sugar without diabetes is rare. Possible causes it names include malnutrition, Addison's disease and a pancreatic tumour.

General treatment for mild lows

Your care team will give you your own plan. In general terms, both the NIDDK and the NHS describe the same pattern: check your glucose if you can, take a fast-acting source of sugar, wait around 10 to 15 minutes, recheck, and repeat if still low. Once glucose is back in range, a longer-lasting snack or your next meal helps keep it there. The NIDDK says people who take medicines that slow carbohydrate digestion may need glucose tablets or gel, because other sources act too slowly. Ask your own doctor which fast-acting options and amounts are right for you.

Severe lows

If a person cannot treat themselves, the NIDDK says glucagon, given by injection or nasal spray, is the treatment of choice, and that family, friends and coworkers should be taught when and how to give it. After giving glucagon, or if none is available, someone should call emergency services right away. The NHS advises not giving food or drink to someone who may not swallow safely, placing them in the recovery position and staying with them. The NIDDK also suggests wearing a medical alert ID.

Prevention

• Check glucose regularly as your care team advises. The NIDDK says a continuous glucose monitor can sound an alarm when levels drop.
• Keep meals and snacks regular and carry fast-acting carbohydrate.
• Check glucose before, during and after exercise and ask your team how to adjust food or medicine.
• If you drink alcohol, eat at the same time.
• Review with your team which medicines can cause lows.
• The NHS advises checking glucose before each journey and every 2 hours while driving, and waiting at least 45 minutes after glucose returns to normal before driving after a low.

When to see a doctor

The NHS advises seeing a GP if you have frequent lows, severe lows, lows at night, or you stop recognising warning signs. People with low blood sugar symptoms who do not have diabetes should also be checked. Contact your diabetes team about any change in pattern.

Call for emergency help if someone with very low blood sugar is unconscious or unresponsive and no glucagon is available, or if they have not recovered within 10 minutes of glucagon, as the NHS describes. In an emergency, call your local emergency number (112 in India, 911 in the United States).

This article is for education only and does not replace advice from your own doctor.