Nitroglycerin tablets work fastest when you take them at the first sign of chest pain or pressure

Nitroglycerin tablets are meant to be taken the moment you feel chest pain, pressure, tightness, or heaviness — not after you wait to see if it goes away. The tablet dissolves under your tongue and reaches your bloodstream within minutes, relaxing the muscles around your blood vessels so blood flows more freely to your heart. Most people feel relief within 5 to 10 minutes.

Your doctor prescribes nitroglycerin because you have a condition — usually angina — where your heart muscle is not getting enough oxygen during stress or exertion. The tablet is your when ready treatment, not a preventive one you take before you know you need it. The exception is if your doctor has told you to take a dose before physical activity you know triggers pain; some people do this as a precaution.

If you take a tablet and the pain does not ease after 5 minutes, take a second tablet. If pain continues 5 minutes after the second tablet, call 911. Do not wait, do not take a third tablet, do not drive yourself to the hospital. Chest pain that does not respond to nitroglycerin can signal a heart attack, and emergency responders need to know when ready.

Key Takeaways

  • Take nitroglycerin the moment chest pain or pressure starts, not after waiting to see if it passes.
  • The tablet dissolves under your tongue and usually brings relief within 5 to 10 minutes.
  • If pain does not ease after one tablet, take a second one 5 minutes later.
  • Call 911 if two tablets do not stop the pain within 10 minutes total, because this can signal a heart attack.
  • Some people take a dose before known triggers like climbing stairs or walking in cold weather, but only if their doctor has said to do so.

How to take the tablet correctly

Sit down before you take the tablet. This prevents you from falling if the medication causes dizziness or a sudden drop in blood pressure — both common side effects. Place the tablet under your tongue and let it dissolve; do not chew it or swallow it whole. The tablet works through the tissue under your tongue, not through your stomach.

If you are wearing a patch of nitroglycerin on your skin, you can still take a tablet under your tongue during an episode. The patch is a slow-release form meant to prevent attacks; the tablet is the fast-acting rescue dose. Tell your doctor if you are using both, because the combination affects how much medication you are receiving.

Keep your tablets in a cool, dark place — not in a hot car, bathroom, or kitchen. Nitroglycerin breaks down quickly in heat and light, and an old or damaged tablet may not work when you need it. Replace your bottle every 3 to 6 months, even if you have not used all the tablets, because they lose strength over time.

Situations where you should take nitroglycerin

Take a tablet if you feel chest pain or pressure during physical activity — climbing stairs, walking uphill, exercising, or even walking against the wind. You may also feel it in your neck, jaw, shoulder, or arm. Some people describe it as heaviness, squeezing, or a tight band across the chest. Any of these sensations warrant a dose.

Emotional stress, anger, or sudden cold can also trigger angina. If you know these situations bring on pain, you can take a tablet before you encounter them — for example, before going outside in winter or before a stressful meeting — but only if your doctor has told you this is appropriate for your condition. Do not use nitroglycerin as a preventive for situations you are not sure about.

Pain that wakes you from sleep or happens while you are resting is less typical for stable angina and should be reported to your doctor. It may signal a change in your condition that needs different treatment. Take a tablet if you have it, but call your doctor the next day to describe what happened.

When not to take nitroglycerin

Do not take nitroglycerin if you have taken a medication for erectile dysfunction in the past 24 hours — drugs like sildenafil (Viagra), tadalafil (Cialis), or vardenafil (Levitra). The combination can cause a dangerous drop in blood pressure. If you take one of these medications regularly, tell your doctor before you are prescribed nitroglycerin, because your doctor may choose a different heart medication instead.

Do not take nitroglycerin if you have low blood pressure (your doctor will tell you what your numbers should be). The tablet lowers blood pressure further, and you may faint or feel severely dizzy. If you are unsure whether your blood pressure is too low, call your doctor or pharmacist before taking a dose.

If you have a headache, do not assume nitroglycerin caused it — headaches are a normal side effect and usually fade within 30 minutes. However, if you develop a severe headache you have never had before while taking nitroglycerin, stop taking it and call your doctor. A sudden new type of headache can signal a serious reaction.

What to expect after you take a tablet

Within a few minutes, you should feel the chest pain or pressure ease. Your heart rate may speed up slightly as your blood vessels relax and your heart works more efficiently. You may feel a slight flushing or warmth in your face and neck, or a mild headache. These are normal and usually pass quickly.

Some people feel lightheaded or dizzy after taking nitroglycerin, especially if they are standing. This is why sitting down before you take the tablet matters. If dizziness is severe or does not fade within a few minutes, lie down and call your doctor. Do not drive or operate machinery until you feel steady.

Keep track of how often you are taking nitroglycerin. If you are using it more than once or twice a week, or if the pain is getting worse or lasting longer, tell your doctor. This can mean your angina is becoming less stable and your treatment plan may need to change.

Storing and carrying nitroglycerin safely

Keep your nitroglycerin bottle in a cool place at room temperature, away from moisture and direct sunlight. A bedroom nightstand or a kitchen cabinet away from the stove works well. Do not store it in a purse or car where heat can damage it. If you carry a bottle with you, keep it in an inside jacket pocket or bag close to your body, not in a back pocket where it may get crushed.

Always carry your nitroglycerin with you when you leave home. Do not leave it at home thinking you will not need it, because angina can strike unexpectedly. If you travel by plane, keep the bottle in your carry-on bag, not in checked luggage. Airport security allows nitroglycerin tablets.

Tell family members and close friends where you keep your nitroglycerin and how to help if you have chest pain. If you become unconscious or unable to speak, they may need to call 911 and tell responders that you have a heart condition and nitroglycerin at home.

When to call your doctor about nitroglycerin use

Contact your doctor if you are taking nitroglycerin more than once or twice a week, if the pain is happening at rest or waking you at night, if the pain is spreading to new areas, or if a tablet is no longer bringing relief as quickly as it used to. Any of these changes means your condition may be shifting and your treatment needs review.

Tell your doctor if you are starting any new medications, including over-the-counter drugs and supplements. Some medications interact with nitroglycerin and can cause dangerous drops in blood pressure or other serious effects. Your pharmacist can also check for interactions when you fill a new prescription.

Report any side effects that worry you — severe headaches, fainting, chest pain that feels different from your usual angina, or shortness of breath that does not improve. These warrant a conversation with your doctor to make sure nitroglycerin is still the right choice for you.

Frequently Asked Questions

Can I take nitroglycerin if I am not sure whether my chest pain is angina?

If you have been prescribed nitroglycerin by your doctor, you have already been diagnosed with a heart condition. Take the tablet if you feel chest pain or pressure. If the pain does not ease after two tablets, call 911. If you have never been prescribed nitroglycerin and you are experiencing chest pain, call 911 or go to an emergency room — do not take someone else's nitroglycerin.

What should I do if I accidentally swallow a nitroglycerin tablet instead of letting it dissolve under my tongue?

The tablet will still work, but it will take longer — 20 to 30 minutes instead of 5 to 10. If you swallow it by accident during chest pain, sit down and wait. If pain does not ease within 10 minutes, take another tablet under your tongue as directed. Call your doctor later to let them know what happened.

Can I take nitroglycerin every day to prevent angina?

Nitroglycerin tablets are a rescue medication for when pain happens, not a daily preventive. Your doctor may prescribe a nitroglycerin patch or a longer-acting medication to prevent attacks, but the tablet is for when ready relief. Taking tablets every day can also cause your body to become less responsive to them. Follow your doctor's instructions on when and how often to use your tablets.

Is it dangerous to take nitroglycerin if my blood pressure is normal?

Nitroglycerin lowers blood pressure as part of how it works, so even normal blood pressure will drop after you take a tablet. This is expected and usually not dangerous. However, if you feel faint or dizzy, lie down when ready. If dizziness is severe or does not pass, call your doctor or 911.

What if my nitroglycerin bottle has expired?

Do not use expired nitroglycerin. The medication loses strength over time and may not work when you need it. Get a new prescription from your doctor and ask your pharmacist to dispose of the old bottle safely. Never throw nitroglycerin in the trash or flush it down the toilet.