Nitroglycerin tablets open blood vessels to reduce chest pain within minutes
Nitroglycerin is a medication that relaxes and widens blood vessels, allowing more blood to flow to your heart. When you place a tablet under your tongue, it dissolves quickly and enters your bloodstream fast — usually within 1 to 3 minutes. This rapid action reduces the pressure your heart has to work against, which stops or prevents chest pain caused by angina (a condition where your heart doesn't get enough oxygen-rich blood).
The tablets come in different strengths, measured in milligrams. Common doses are 0.3 mg, 0.4 mg, and 0.6 mg. Your doctor prescribes the strength based on your heart condition and how your body responds. The tablet works only on the vessels in your body — it does not repair the underlying heart problem, but it gives your heart temporary relief by making its job easier.
Nitroglycerin is not a long-term fix. It is a rescue medication you use when chest pain starts or when you know you are about to do something that triggers it (like climbing stairs or walking in cold weather). Some people take a tablet before physical activity to prevent pain from happening at all.
Key Takeaways
- Nitroglycerin tablets dissolve under your tongue and widen blood vessels to let more blood reach your heart, stopping chest pain in 1 to 3 minutes.
- The medication is a rescue treatment for acute chest pain, not a daily preventive medicine, though you can take it before activity that usually triggers pain.
- If chest pain does not go away after one tablet, take a second tablet 5 minutes later, and if it still does not stop after a third tablet 5 minutes after that, call 911 when ready.
- Nitroglycerin can cause headaches, dizziness, or a drop in blood pressure, and it should not be mixed with certain other medications or erectile dysfunction drugs.
- Store tablets in a cool, dark place in their original amber bottle, and replace them every 3 to 6 months because they lose strength over time.
How to use nitroglycerin tablets 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. Place one tablet under your tongue and let it dissolve — do not swallow it whole or chew it. The tablet should dissolve completely within a few minutes.
If the chest pain does not stop after 5 minutes, take a second tablet the same way. Wait another 5 minutes. If pain is still present after a third tablet (taken 5 minutes after the second), call 911 when ready. Do not keep taking more tablets hoping the pain will go away. Three tablets in 15 minutes is the standard limit, and if they do not work, you may be having a heart attack and need emergency care.
Some people carry nitroglycerin with them at all times because they never know when chest pain will strike. Others keep it at home and take it before known triggers. Your doctor will tell you how often you should expect to use it. If you find yourself using it more than once or twice a week, tell your doctor — it may mean your heart condition is getting worse or your current dose is not strong enough.
Side effects and what to expect
The most common side effect is a headache, which can range from mild to severe. This happens because nitroglycerin widens all your blood vessels, not just the ones in your heart, so blood vessels in your head expand too. The headache usually fades within 30 minutes to an hour. Taking the tablet with food or water sometimes reduces headache severity.
You may also feel dizzy, lightheaded, or flushed (warm and red in the face). Your blood pressure can drop temporarily, which is why sitting down before taking the tablet matters. If dizziness is severe or does not pass within a few minutes, lie down with your feet raised higher than your head to help blood flow back to your brain.
Less common side effects include nausea, rapid heartbeat, or a burning sensation under your tongue. These usually go away quickly. If side effects are bothersome or do not fade, talk to your doctor — they may adjust your dose or switch you to a different form of nitroglycerin (such as a spray or patch).
Medications and substances to avoid with nitroglycerin
Never take nitroglycerin with erectile dysfunction medications like sildenafil (Viagra), tadalafil (Cialis), or vardenafil (Levitra). The combination can cause a dangerous drop in blood pressure that may lead to a heart attack or stroke. This warning applies even if you take the erectile dysfunction drug hours before or after the nitroglycerin.
Tell your doctor about all medications you take, including over-the-counter drugs and supplements. Certain blood pressure medications, pain relievers, and other heart drugs can interact with nitroglycerin. Your doctor will review your full medication list to make sure nitroglycerin is safe for you.
Alcohol can also lower your blood pressure and increase dizziness when combined with nitroglycerin. Avoid drinking alcohol shortly before or after taking a tablet. If you drink regularly, mention this to your doctor so they can monitor you more closely.
Storage and shelf life of nitroglycerin tablets
Nitroglycerin tablets lose strength over time, especially when exposed to light, heat, or moisture. Store them in the original amber (brown) bottle with the cap tightly closed. Keep the bottle in a cool, dark place — not in a bathroom medicine cabinet where humidity from showers can damage them, and not in a car where heat builds up.
Check the expiration date on your bottle. Most nitroglycerin tablets expire 3 to 6 months after the pharmacy fills your prescription, even if the printed expiration date is later. Once they expire or lose potency, they may not work when you need them. Ask your pharmacist when your tablets were filled, and mark your calendar to replace them before they expire.
If your tablets no longer produce a burning or tingling sensation under your tongue, they have likely lost strength and should be replaced. Some people carry a spare bottle in a different location (like a purse or jacket pocket) so they always have access, but remember to rotate these bottles too and check expiration dates regularly.
When nitroglycerin is not enough
If you need nitroglycerin more than once or twice a week, your doctor may prescribe a long-acting medication to take daily. These include beta-blockers, calcium channel blockers, or long-acting nitrates. These daily medications reduce how often chest pain happens and how severe it is, while nitroglycerin remains your rescue option for acute pain.
Some people also benefit from lifestyle changes alongside medication. Your doctor may recommend cardiac rehabilitation (supervised exercise and education), dietary changes to lower cholesterol, quitting smoking, or stress management. These do not replace nitroglycerin but work together with it to improve heart health over time.
If you have never had chest pain before and suddenly experience it, do not assume nitroglycerin will solve it. Seek medical attention to find out what is causing the pain. Chest pain can come from many sources — some serious, some not — and only a doctor can diagnose the cause and recommend the right treatment.
Frequently Asked Questions
How fast does nitroglycerin work?
Nitroglycerin tablets usually start working within 1 to 3 minutes because they dissolve under your tongue and enter your bloodstream quickly. Peak relief typically comes within 5 to 10 minutes. If you do not feel relief within 5 minutes, take a second tablet.
Can I take nitroglycerin every day?
Nitroglycerin tablets are designed as rescue medication for acute chest pain, not daily prevention. However, you can take one tablet before activities you know will trigger pain. If you need it daily, your doctor will likely prescribe a long-acting preventive medication instead, because your body can build tolerance to nitroglycerin with constant use.
What should I do if nitroglycerin does not relieve my chest pain?
Take a second tablet after 5 minutes, then a third after another 5 minutes if needed. If three tablets over 15 minutes do not stop the pain, call 911 when ready. Do not drive yourself to the hospital — emergency responders can begin treatment in the ambulance and alert the hospital you are coming.
Can I use an expired nitroglycerin tablet?
Expired or old nitroglycerin tablets may not work when you need them because the medication loses strength over time. Always replace your tablets before the expiration date. If you only have expired tablets available during a chest pain emergency, take one and call 911 — do not wait to see if it works.
Does nitroglycerin cure heart disease?
No. Nitroglycerin relieves the symptoms of chest pain by improving blood flow to your heart, but it does not repair the underlying heart condition or prevent future heart attacks. It is a symptom-relief medication, not a cure. Your doctor will recommend other treatments to address the root cause of your heart problem.