Hypoglycaemia in diabetes

This page from Great Ormond Street Hospital (GOSH) explains about hypoglycaemia when you have diabetes and how you should treat it. 


  • Hypoglycaemia or ‘hypo’ is the word used to describe a low blood glucose level
  • The blood glucose will be 3.9mmol/l or below

What causes hypos?

  • Too much insulin
  • Not enough food
  • Extra activity/exercise
  • Poor absorption of food
  • Some medications
  • Alcohol and drugs


  • These can be varied and people may experience very different symptoms
  • Common symptoms that occur are: hunger, feeling shaky, dizzy, sweating, headache, feeling angry and looking pale
  • If your blood glucose drops below 2.8mmol/l, the brain is not supplied with enough glucose and you may struggle to concentrate and/or your behaviour may change

How do I treat a hypo?

The 15 Rule

  • Treat a blood glucose of 3.9mmol/l or below (even if you feel alright)
  • Treatment is by taking a fast-acting carbohydrate by mouth
  • Treat as soon as possible, to prevent your blood glucose dropping even further. Correct treatment will also prevent your blood levels rising too high afterwards (rebound hyperglycaemia)
  • Carry hypo treatment with you at all times
  • You will need about 15g of fast-acting carbohydrate, this may vary depending on your age
Lucozade® 100mls or ½ cup
Glucose tablets 3 to 5 tablets = 3g carbohydrate
Non-diet fizzy drink 150 to 200mls = 1 mini can
Fruit juice 150 to 200mls = 1 small carton
Glucogel® 1 to 2 tubes - each tube has 10g
Jelly sweets such as Haribo®, Fruit Pastilles® or wine gums 1 very small packet or 4 to 6 sweets
  • Once you have treated the hypo, wait for 15 minutes and re-test. The aim is to restore the blood glucose back to a normal level, aiming to reach 5.6mmol/L.
  • Chocolate, biscuits, milk, bread, cakes and fruit are not suitable hypo treatments as the glucose is absorbed too slowly. Your blood glucose could continue to drop while the food is being absorbed
  • You should not need to eat more after treating your hypo. If you have a further hypo you may wish to consider eating some starchy carbohydrate.
  • If this happens regularly you should contact your diabetes team as your insulin may need adjusting.
  • If the hypo is just before a meal it is important to treat the hypo before eating. You may wish to consider taking insulin after eating in this situation.

Severe hypoglycaemia

  • This is uncommon
  • It is when your blood glucose has dropped too low and your brain cannot work properly
  • If you are conscious, then use the 15 rule
  • If you are unconscious, then nothing should be put in your mouth. You should be given the glucagon injection. A parent or carer can do this or they can call an ambulance and the paramedic will be able to give it instead. Glucagon works within 10 minutes
  • Once you have regained consciousness, you should eat some starchy carbohydrate.
  • After having the glucagon injection there is a risk of further hypoglycaemia so you need to be reviewed at your local hospital.
  • Any severe hypoglycaemia should be discussed with your specialist diabetes team to prevent it from happening again
The Children and Young People’s Diabetes Team in collaboration with the Child and Family Information GroupOctober 20152015C0203
Please note this is a generic GOSH information sheet so should not be used for the diagnosis or treatment of any medical condition. If you have specific questions about how this relates to your child, please ask your doctor.