What counts as low?
A glucose below 70 mg/dL (3.9 mmol/L) is considered low. Below 54 mg/dL is serious. Some people feel symptoms at higher levels if their sugars have been running high.
Symptoms
- Shaking, sweating and a pounding heart
- Hunger, anxiety or irritability
- Headache, blurred vision or difficulty concentrating
- In severe cases: confusion, seizures or loss of consciousness
Common causes in people with diabetes
- Insulin or sulfonylurea tablets, especially if the dose is too high
- Missed or delayed meals
- Unusual exercise, or alcohol
- Reduced kidney function, which makes some medicines last longer
Low sugar without diabetes is less common. Causes include alcohol, some medicines, liver or kidney disease, hormone deficiencies such as cortisol, and rarely an insulin-producing tumour.
What to do
If the person is awake and can swallow, give about 15 g of fast-acting sugar: glucose tablets, about 150 ml of fruit juice or a regular soft drink, or three teaspoons of sugar or honey. Recheck after 15 minutes and repeat if still below 70 mg/dL. Once it recovers, have a snack or meal.
If the person is drowsy, confused or unconscious, do not put food or drink in the mouth. Call emergency services (108) and use glucagon if it has been prescribed.
Preventing lows
- Do not skip meals when on insulin or sulfonylureas
- Check sugars before driving and before exercise
- Always carry fast-acting sugar
- Tell your doctor about any low; the dose may need changing
When to see a specialist
See a doctor if you have frequent lows, lows at night, lows with no warning symptoms, or a low sugar without having diabetes.
What to do when glucose is low
If an adult who is awake and able to swallow has a glucose reading below 70 mg/dL, take about 15 grams of fast-acting carbohydrate, such as glucose tablets according to the pack, or approximately 150 mL of regular fruit juice or a sugary drink. Recheck after 15 minutes. If it is still below 70 mg/dL, repeat. Once corrected, have a meal or snack if the next meal is not soon, particularly if the medicine causing the low is still active. Your clinician may give you a different plan.
Do not give food, drink or tablets by mouth to someone who is unconscious, having a seizure or unable to swallow safely. Place them on their side, use prescribed glucagon if available and someone is trained to give it, and seek emergency medical help.
Why do lows keep happening?
Repeated episodes may mean that insulin or sulfonylurea doses, meal timing, activity, alcohol intake or kidney function need review. Do not simply compensate by eating extra calories throughout the day. Record the time of each episode, the glucose value, medicines, meals and activity so the treatment plan can be adjusted safely.
This guide is for general educational purposes and does not replace individual medical advice, diagnosis or treatment. Consult your doctor for advice specific to your health.