Nitroglycerin Side Effects Overview

Nitroglycerin is a nitrate vasodilator that works by relaxing blood vessels to improve blood flow and reduce the heart's workload. While it's highly effective for treating and preventing angina, like all medications it comes with potential side effects. Understanding what to expect can help you use Nitroglycerin safely and know when something requires medical attention.

If you're new to this medication, you may want to start with our guide on what Nitroglycerin is and how it's used.

Common Side Effects of Nitroglycerin

Most side effects of Nitroglycerin are related to its blood vessel-relaxing mechanism. These are generally mild and often improve as your body adjusts to the medication.

Headache (Most Common)

Headache is the most frequently reported side effect, affecting up to 50% of patients. Nitroglycerin dilates blood vessels, including those in the brain, which can trigger headaches. This is sometimes called a "nitrate headache."

How to manage it:

• Over-the-counter pain relievers like acetaminophen (Tylenol) can help
• Headaches often decrease in frequency and severity over time as your body adjusts
• Taking the medication with food may reduce headache intensity for oral forms
• If headaches are severe or persistent, talk to your doctor about adjusting your dose

Dizziness and Lightheadedness

Because Nitroglycerin lowers blood pressure, dizziness is common — especially when standing up quickly (orthostatic hypotension). This is more likely with your first few doses or after a dose increase.

How to manage it:

• Stand up slowly from sitting or lying positions
• Sit or lie down if you feel dizzy after taking Nitroglycerin
• Avoid driving or operating machinery until you know how Nitroglycerin affects you
• Stay hydrated throughout the day

Flushing

Warmth and redness in the face, neck, or chest can occur as blood vessels dilate. This is harmless and typically short-lived.

Nausea

Some patients experience mild nausea, particularly with sublingual tablets or spray formulations. This usually resolves on its own.

Application Site Irritation (Patches)

If you use Nitroglycerin transdermal patches (Nitro-Dur, Minitran), you may experience redness, itching, or mild irritation where the patch is applied. Rotating application sites daily helps minimize this.

Serious Side Effects: When to Call Your Doctor

While most Nitroglycerin side effects are mild, some require prompt medical attention.

Severe Hypotension (Dangerously Low Blood Pressure)

Nitroglycerin can cause blood pressure to drop too low, leading to:

• Severe dizziness or fainting (syncope)
• Blurred vision
• Confusion
• Cold, clammy skin
• Rapid heartbeat

What to do: If you experience fainting or symptoms of severely low blood pressure, lie down with your legs elevated and call your doctor immediately. If symptoms are severe, call 911.

Reflex Tachycardia

When blood pressure drops, your heart may compensate by beating faster. While mild increases in heart rate are normal, significant or sustained rapid heartbeat should be reported to your doctor.

Methemoglobinemia (Rare)

In rare cases, usually with very high doses, Nitroglycerin can cause methemoglobinemia — a condition where the blood can't carry oxygen effectively. Symptoms include:

• Bluish coloring of lips, fingernails, or skin (cyanosis)
• Shortness of breath
• Fatigue and weakness
• Headache and dizziness

This is a medical emergency. Seek immediate care if you notice these symptoms.

Tolerance

With continuous use (especially patches worn 24 hours), your body can develop tolerance to Nitroglycerin, making it less effective. This is why doctors prescribe a nitrate-free interval — typically removing patches for 10-12 hours overnight. For more on how this works, see our article on Nitroglycerin's mechanism of action.

Rebound Angina

Stopping Nitroglycerin suddenly — particularly long-acting forms like patches or sustained-release capsules — can cause worsening angina. Never stop Nitroglycerin abruptly without your doctor's guidance.

Side Effects by Formulation

Different forms of Nitroglycerin may cause slightly different side effect profiles:

• Sublingual tablets and spray — More likely to cause sudden dizziness and headache due to rapid absorption. Effects are short-lived (minutes to an hour).
• Transdermal patches — Slower onset of side effects but can cause persistent low-grade headache and skin irritation. Tolerance is a bigger concern.
• Sustained-release capsules — Side effects similar to patches but without skin irritation.
• Topical ointment — Can cause headache and dizziness; skin irritation at application site.

Drug Interactions That Can Worsen Side Effects

Certain medications and substances can dramatically increase Nitroglycerin's side effects, particularly hypotension. The most critical interactions include:

• PDE5 inhibitors (sildenafil/Viagra, tadalafil/Cialis, vardenafil/Levitra) — CONTRAINDICATED. Can cause severe, potentially fatal drops in blood pressure.
• Alcohol — Significantly increases risk of hypotension, dizziness, and fainting.
• Other blood pressure medications — May cause additive blood pressure lowering.

For a complete list, read our detailed guide on Nitroglycerin drug interactions.

Tips for Minimizing Side Effects

1. Start low, go slow — Your doctor will typically start you on the lowest effective dose
2. Stay hydrated — Adequate fluid intake helps maintain blood pressure
3. Avoid alcohol — Even moderate amounts can worsen hypotension
4. Change positions slowly — Rise gradually from sitting or lying down
5. Follow the nitrate-free interval — Remove patches at bedtime to prevent tolerance
6. Keep a side effect diary — Track symptoms to discuss with your doctor
7. Don't skip doses or stop suddenly — This can cause rebound angina

When to Seek Emergency Care

Call 911 or go to the emergency room if you experience:

• Fainting or loss of consciousness
• Chest pain that worsens or doesn't improve after 3 sublingual tablets in 15 minutes
• Blue discoloration of lips or fingernails
• Severe difficulty breathing
• Irregular or very rapid heartbeat
• Signs of allergic reaction (rash, swelling of face/throat, difficulty breathing)

Talk to Your Doctor

Side effects are a normal part of any medication, and most Nitroglycerin side effects are manageable. If side effects are affecting your quality of life, your doctor may adjust your dose, switch formulations, or explore alternative medications.

Having trouble finding Nitroglycerin at your pharmacy? Learn how to find Nitroglycerin in stock near you or use MedFinder to check pharmacy availability.