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Glyceryl trinitrate (GTN)

Patient information A-Z


Glyceryl trinitrate (GTN) is used to treat and prevent angina pain. Angina is chest pain which occurs when the heart muscle tries to work without enough oxygen. Physical activity, sudden cold or stress can bring on angina. You can use your GTN a few minutes before any activity that you know brings on your angina pain.

Taking your GTN

GTN is available as either a spray or sublingual tablets (300mcg or 500mcg).


Spray once or twice under the tongue, whilst holding your breath. Close your mouth immediately. Do not inhale the spray.

Sublingual tablets

Put one or two tablets under the tongue if chest pain occurs. Do not swallow the tablet.

The spray or tablets should work almost immediately (within two to three minutes). If your chest pain persists, take a second dose after five minutes. If your chest pain still persists, take a third dose after five minutes. If you still have chest pain after three doses of GTN, call 999 and ask for an ambulance as you may be having a heart attack.

Problems to watch for

The most common side effects are a slight headache, dizziness, flushing and faintness. These are usually mild and wear off quickly.

Storage of your tablets

Always keep the tablets in the original glass bottle. Never transfer tablets to another bottle.

Throw away any unused tablets eight weeks after opening the bottle (write the date when the bottle is first opened on the bottle), and obtain a new supply of tablets from your doctor.

Other important information

Always keep a supply of spray or tablets with you at all times.

We are smoke-free

Smoking is not allowed anywhere on the hospital campus. For advice and support in quitting, contact your GP or the free NHS stop smoking helpline on 0800 169 0 169.

Other formats

Help accessing this information in other formats is available. To find out more about the services we provide, please visit our patient information help page (see link below) or telephone 01223 256998.

Contact us

Cambridge University Hospitals
NHS Foundation Trust
Hills Road, Cambridge

Telephone +44 (0)1223 245151