What nitroglycerin tablets do and when to take them
Nitroglycerin tablets work by relaxing the blood vessels in your heart, which increases blood flow and reduces the workload on your heart muscle. This eases chest pain (angina) within a few minutes. If your doctor has prescribed nitroglycerin tablets for you, they are meant to be taken at the first sign of chest pain or pressure—not after you wait to see if it goes away on its own.
The tablet dissolves under your tongue, where it enters your bloodstream quickly. You should feel relief within 5 to 10 minutes. If the pain does not improve after one tablet, take a second tablet 5 minutes later. If pain continues after a third tablet taken 5 minutes after the second, call 911 when ready—do not drive yourself to the hospital.
Key Takeaways
- Place one nitroglycerin tablet under your tongue at the first sign of chest pain and let it dissolve completely without chewing or swallowing.
- If pain does not ease within 5 minutes, take a second tablet; if it persists after a third tablet 5 minutes later, call 911.
- Keep your tablets in a cool, dark place in their original brown or amber bottle, and replace them every 3 to 6 months because they lose strength over time.
- Always carry your nitroglycerin with you, and tell people around you where it is kept in case you need help during an episode.
- Nitroglycerin can cause headache, dizziness, or a drop in blood pressure; sit down when you take it to avoid falling.
The correct steps for taking a tablet
Stop what you are doing and sit down when ready. Remaining upright while taking nitroglycerin can cause dizziness or fainting because the medication lowers blood pressure. Once seated, remove one tablet from your bottle and place it under your tongue, slightly to one side. Do not chew it, crush it, or swallow it whole—the tablet must dissolve in the tissue under your tongue so it can enter your bloodstream directly.
Close your mouth and breathe normally. The tablet will dissolve on its own within a few minutes. You may taste a slight burning or tingling sensation under your tongue; this is normal and means the tablet is working. Do not eat, drink, or smoke while the tablet is dissolving, as these actions can interfere with how quickly it works.
Sit quietly and wait. Most people feel relief within 5 to 10 minutes. If you do not feel better after 5 minutes, take a second tablet from your bottle and place it under your tongue the same way. Wait another 5 minutes. If the pain is still there, take a third tablet. If you have taken three tablets over 15 minutes and the pain has not eased, call 911 or have someone drive you to the nearest emergency room.
Storage and shelf life matter more than most people realize
Nitroglycerin tablets lose their strength quickly and must be stored correctly to remain effective. Keep your bottle in a cool, dark, dry place—not in a bathroom medicine cabinet where heat and humidity break down the medication. The original brown or amber bottle protects the tablets from light, which also degrades them. Never transfer your nitroglycerin to a plastic pill organizer or clear container.
Check the expiration date on your bottle. If your tablets have expired or if you cannot remember when you last filled the prescription, ask your pharmacist for a new bottle. Most nitroglycerin prescriptions should be refilled every 3 to 6 months, even if you have not used all the tablets, because the remaining ones may no longer work when you need them. A tablet that has lost its strength will not relieve your chest pain, and you may waste precious time thinking it will kick in.
Keep one bottle with you at all times—in your pocket, purse, or bag. If you spend a lot of time away from home, keep a second bottle in your car or at work. Tell family members, coworkers, or close friends where your nitroglycerin is kept so they can help you take it if you are unable to reach it yourself.
Side effects and what to expect
Nitroglycerin commonly causes a headache, especially the first few times you take it. This headache is usually mild and goes away within 30 minutes to an hour. Over-the-counter pain relievers like acetaminophen or ibuprofen can help, though some people find that the headache lessens if they take nitroglycerin regularly as prescribed.
You may also feel lightheaded, dizzy, or flushed (warm and red in the face). This happens because nitroglycerin lowers your blood pressure. This is why sitting down before you take the tablet is so important—standing up too quickly after taking it can cause you to faint. If you feel very dizzy or your vision blurs, lie down with your feet elevated and call your doctor.
Do not take nitroglycerin if you have used certain medications for erectile dysfunction (such as sildenafil, tadalafil, or vardenafil) within the past 24 to 48 hours. The combination can cause a dangerous drop in blood pressure. Tell your doctor about all medications and supplements you take before starting nitroglycerin.
When to call your doctor instead of taking a tablet
If you are having chest pain more often than usual, or if the pain is different from your normal angina—for example, if it happens at rest or is more severe—do not assume a nitroglycerin tablet will handle it. Call your doctor or go to the emergency room. A change in your chest pain pattern can signal that your heart condition is worsening and you may need different treatment.
If you have taken nitroglycerin as prescribed but the pain is not going away, or if you are running out of tablets before your next refill, contact your doctor. Do not skip doses or stretch out your supply. Your doctor may need to adjust your prescription or add another medication to prevent angina from happening in the first place.
Nitroglycerin for prevention versus relief
Some doctors prescribe nitroglycerin in a different form—a patch, spray, or longer-acting tablet—to be taken regularly to prevent angina from happening. This is different from the fast-acting tablet you take when pain starts. If your doctor has given you both types, make sure you understand which is which. The tablet under your tongue is for acute pain; the other form is for prevention and should be taken on a schedule whether or not you have pain.
If you use a nitroglycerin spray instead of tablets, the steps are similar: spray one or two doses under your tongue at the first sign of chest pain, sit down, and wait 5 to 10 minutes. If pain continues, call 911. Ask your pharmacist or doctor to show you how to use whichever form you have been prescribed, because using it correctly makes the difference between fast relief and wasted time.
What to do if you take a tablet by mistake
If you accidentally take a nitroglycerin tablet when you do not have chest pain, do not panic. The worst that usually happens is a headache and some dizziness. Sit down, drink water, and rest for a few minutes. The effects wear off within 30 minutes to an hour. You do not need to go to the hospital unless you feel very unwell or your symptoms do not improve.
If a child or pet swallows a nitroglycerin tablet, call Poison Control at 1-800-222-1222 right away. They will tell you what to do based on the child's or pet's age and weight. Keep your nitroglycerin bottle out of reach of children and pets, and never leave tablets sitting out on a table or counter.
Frequently Asked Questions
How long does a nitroglycerin tablet take to work?
Most people feel relief within 5 to 10 minutes of placing the tablet under their tongue. If you do not feel better after 5 minutes, take a second tablet. If three tablets over 15 minutes do not relieve the pain, call 911.
Can I chew or swallow a nitroglycerin tablet?
No. The tablet must dissolve under your tongue to work quickly. Chewing or swallowing it sends it to your stomach, where it is absorbed much more slowly and may not relieve your pain in time. Always place it under your tongue and let it dissolve on its own.
What should I do if my nitroglycerin tablets have expired?
Expired tablets may not work when you need them. Ask your pharmacist for a new prescription and bottle. Even if you have not used all the tablets in your current bottle, replace it every 3 to 6 months to may support they are still effective.
Can I take nitroglycerin with other heart medications?
Most heart medications work safely with nitroglycerin, but some do not. Tell your doctor about all medications you take, especially erectile dysfunction drugs, which can cause a dangerous drop in blood pressure when combined with nitroglycerin.
Is it okay to drive after taking a nitroglycerin tablet?
No. Nitroglycerin can cause dizziness and lower your blood pressure, which impairs your ability to drive safely. Sit down and rest for at least 10 to 15 minutes after taking a tablet before doing anything that requires alertness or coordination.