Hypoglycaemia in diabetes

This page from Great Ormond Street Hospital (GOSH) explains about hypoglycaemia when someone has diabetes and how it should be treated.


  • 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 blood glucose drops below 2.8mmol/l, the brain is not supplied with enough glucose and people may struggle to concentrate and/or their behaviour may change

How does someone treat a hypo?

The 15 Rule

  • Treat a blood glucose of 3.9mmol/l or below (even if they feel all right)
  • Treatment is by taking a fast-acting carbohydrate by mouth
  • Treat as soon as possible, to prevent blood glucose dropping even further. Correct treatment will also prevent blood levels rising too high afterwards (rebound hyperglycaemia)
  • Carry hypo treatment with them at all times
  • They will need about 15g of fast-acting carbohydrate; this may vary depending on their age
Fast-actingcarbohydrate Quantity
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 the hypo has been treated, they should 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. The blood glucose could continue to drop while the food is being absorbed
  • They should not need to eat more after treating their hypo. If they have a further hypo they may wish to consider eating some starchy carbohydrate.
  • If this happens regularly they should contact their diabetes team as their insulin may need adjusting.
  • If the hypo is just before a meal it is important to treat the hypo before eating. They may wish to consider taking insulin after eating in this situation.

Severe hypoglycaemia

  • This is uncommon
  • It is when blood glucose has dropped too low and your brain cannot work properly
  • If they are conscious, they should use the 15 rule
  • If they are unconscious, then nothing should be put in their mouth. They 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 they have regained consciousness, they should eat some starchy carbohydrate.
  • After having the glucagon injection there is a risk of further hypoglycaemia so they need to be reviewed at their local hospital.
  • Any severe hypoglycaemia should be discussed with their specialist diabetes team to prevent it from happening again
Compiled by:
The Children and Young People’s Diabetes Team in collaboration with the Child and Family Information Group
Last review date:
December 2019