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
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 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: 
October 2015


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.