What to Know About Paxlovid Side Effects Before You Start Treatment

If your doctor has prescribed Paxlovid (Nirmatrelvir/Ritonavir) for COVID-19, you're probably wondering what side effects to expect. The good news: most people tolerate Paxlovid well, and the most common side effects are mild and temporary. But there are a few things you should watch for.

This guide covers the common side effects, the serious ones that need medical attention, and practical tips for managing discomfort during your 5-day treatment course.

What Is Paxlovid?

Paxlovid is an oral antiviral medication made by Pfizer that treats mild-to-moderate COVID-19 in adults at high risk for severe illness. It contains two active ingredients: Nirmatrelvir, which blocks the virus from replicating, and Ritonavir, which slows the breakdown of Nirmatrelvir so it stays active in your body longer. To learn more about how the medication works, see our complete guide to Paxlovid.

Common Side Effects

These side effects are generally mild and tend to go away on their own after you finish the 5-day course:

• Dysgeusia (altered or metallic taste) — This is the most commonly reported side effect, affecting up to 6% of patients. Many people describe it as a bitter, metallic, or "chemical" taste in the mouth that can last throughout treatment.
• Diarrhea — Occurs in approximately 3% of patients. Usually mild and manageable.
• Hypertension (elevated blood pressure) — Some patients experience temporary blood pressure increases during treatment.
• Myalgia (muscle aches) — Mild muscle pain or soreness may occur, though this can also overlap with COVID-19 symptoms themselves.
• Headache — Relatively common and usually mild.
• Nausea — Some patients feel mildly nauseous, particularly when taking the medication on an empty stomach.

Serious Side Effects

While rare, these side effects require immediate medical attention. Call your doctor or go to the emergency room if you experience:

• Signs of a severe allergic reaction — difficulty breathing, swelling of the face, lips, tongue, or throat, severe rash or hives, or feeling faint. Anaphylaxis and angioedema have been reported.
• Signs of liver problems (hepatotoxicity) — yellowing of the skin or whites of the eyes (jaundice), dark urine, pale stools, severe nausea or vomiting, or pain in the upper right area of your abdomen.
• Symptoms of dangerous drug interactions — Because ritonavir is a potent CYP3A4 inhibitor, it can dramatically increase blood levels of other medications you take. Signs of a dangerous interaction include unusual heart rhythms, extreme drowsiness, severe muscle pain, difficulty breathing, or unexplained bleeding. Review our drug interactions guide for details.

Side Effects in Specific Populations

Kidney Impairment

If you have moderate kidney impairment (eGFR 30–59 mL/min), your doctor should prescribe a reduced dose of 150 mg Nirmatrelvir with 100 mg Ritonavir twice daily. Paxlovid is not recommended for patients with severe kidney impairment (eGFR below 30 mL/min). Using the standard dose with impaired kidneys can increase your risk of side effects.

Liver Impairment

No dose adjustment is needed for mild-to-moderate liver impairment. However, Paxlovid is not recommended for patients with severe liver problems. If you have a history of liver disease, tell your doctor before starting treatment.

Pregnancy and Breastfeeding

There is limited data on Paxlovid use during pregnancy. Your doctor will weigh the potential benefits against the risks. Breastfeeding is not recommended during Paxlovid treatment.

Older Adults

Adults over 65 are among the most common Paxlovid users because of their higher risk for severe COVID-19. Side effects in older adults are generally similar to those in younger patients, but kidney function should be checked since it naturally declines with age.

How to Manage Common Side Effects

Here are practical tips for getting through the 5-day course more comfortably:

For the Metallic Taste

• Suck on sugar-free mints or hard candies between doses
• Chew gum to help mask the taste
• Try eating citrus fruits or drinking lemonade
• Brush your teeth and tongue more frequently
• Know that it's temporary — the taste typically fades within a day or two of finishing treatment

For Diarrhea

• Stay well hydrated with water and electrolyte drinks
• Eat bland, easy-to-digest foods (rice, toast, bananas)
• Avoid dairy, spicy, and fatty foods during treatment
• Over-the-counter anti-diarrheal medications like loperamide (Imodium) can help — but check with your pharmacist first

For Nausea

• Take Paxlovid with a small meal or snack
• Eat smaller, more frequent meals throughout the day
• Avoid strong-smelling foods
• Ginger tea or ginger chews may help settle your stomach

For Headache and Muscle Aches

• Acetaminophen (Tylenol) is generally safe to take with Paxlovid
• Stay hydrated and rest as much as possible
• Consult your doctor before taking NSAIDs like ibuprofen, as interactions may vary

Final Thoughts

Most people who take Paxlovid experience either no side effects or only mild ones — the metallic taste and occasional diarrhea being the most common. These are temporary and go away after the 5-day course is complete.

The most important thing is to not stop taking Paxlovid early because of mild side effects. Completing the full course gives you the best protection against severe COVID-19. If you experience anything serious — especially signs of an allergic reaction or liver problems — contact your doctor immediately.

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