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Low blood sugar (hypoglycaemia)

Hypoglycaemia, also called a hypo, means you have a low blood sugar (glucose) level. Anything less than 4 is low. It happens mainly if you inject insulin, but it can also happen with some tablets.


A hypo can happen quickly and you need to treat it immediately. If you don't treat your hypo, you can become unconscious.

Wait 10 minutes, then test your blood sugar again.

What causes a hypo?

You can have a hypo if you:

What are the warning signs of a hypo?

If you are having a hypo, you are like to have some of the following symptoms:

You may also feel:

What else should I know about hypos?

You can have a hypo without having any symptoms. This can happen if you haven't eaten for a long time, have given yourself too much insulin, or exercised hard without having any extra food. If you think there's a danger you might be having a hypo, even without symptoms, test your blood sugar level.

You should always carry a hypo treatment with you. If you don't treat a hypo, you may lose consciousness, or have a fit or seizure.

If you have a hypo before a meal, you should follow the instructions above to get your blood sugar level above 3.5. Then, have insulin either just before your meal (Penmix) or straight after it (Apidra, Humalog, Humalog Mix 25, Humalog Mix 50, NovoMix 30 or NovoRapid).

You might have symptoms of a hypo when your blood sugar level is not low if:


Tell your family and friends how to treat a hypo, so they can help you if you can't help yourself. If you are unconscious they should:

You risk losing your licence if you drive when you are having a hypo. Tell your doctor or diabetes nurse if you keep having hypos.

On the next page: Guidelines for giving glucagon

Written by Christchurch Diabetes Centre. Adapted by HealthInfo clinical advisers. Endorsed by clinical director, Diabetes Services, Canterbury DHB. Last reviewed May 2016.


Jelly beans image courtesy of Bill Longshaw at

Page reference: 178645

Review key: HIDIA-21832