Lagevrio Side Effects: What to Expect and When to Call Your Doctor

Lagevrio (molnupiravir) is generally well-tolerated, and most patients complete the 5-day course without significant difficulty. But like any medication, it can cause side effects — and some require immediate medical attention. Here's everything you need to know.

Common Side Effects of Lagevrio

In the MOVe-OUT clinical trial and real-world use, the most commonly reported side effects of Lagevrio were:

Diarrhea — the most frequently reported side effect

Nausea — often mild and manageable

Dizziness — may also be worsened by alcohol (avoid heavy drinking during treatment)

These side effects are generally mild and tend to improve as your body adjusts to the medication. Tell your healthcare provider if they bother you or don't go away.

Serious Side Effects: When to Seek Help Immediately

Although rare, Lagevrio can cause serious side effects that require immediate medical attention:

Severe allergic reaction (anaphylaxis): Symptoms include feeling faint, trouble breathing, swelling of the face or tongue, difficulty swallowing, itchy rash or hives. Stop taking Lagevrio and get emergency help immediately.

Worsening symptoms: Shortness of breath, chest pain, confusion, or severe fatigue that gets worse while on treatment should prompt an immediate call to your provider.

The Most Important Warning: Pregnancy

Lagevrio carries a boxed warning — the FDA's strongest safety label — regarding the risk of fetal harm. Animal studies showed that molnupiravir caused birth defects and fetal death at doses several times higher than the human therapeutic dose. While no human data are available, Lagevrio is not recommended during pregnancy.

If you can become pregnant, use effective contraception during treatment and for 4 days after the last dose. If your partner can become pregnant, use effective contraception during treatment and for 3 months after the last dose.

Breastfeeding Precautions

Breastfeeding is not recommended during Lagevrio treatment and for 4 days after the final dose. Animal studies detected the active metabolite in the milk of nursing animals. If you are breastfeeding, discuss the risks with your provider. You may consider temporarily stopping breastfeeding and pumping and discarding breast milk during treatment and for 4 days after.

Age Restriction and Bone/Cartilage Warning

Lagevrio is not authorized for use in patients under 18 years of age. The concern is potential effects on bone and cartilage growth in developing individuals. In animal studies, molnupiravir caused cartilage and bone toxicity at high doses. For this reason, the EUA explicitly excludes pediatric patients.

Does Lagevrio Interact With Other Medications?

One of Lagevrio's major advantages is its lack of known drug interactions. No formal drug-drug interaction studies have been conducted, but based on available data, no clinically significant interactions have been identified. This makes Lagevrio particularly useful for patients on complex medication regimens where Paxlovid — which has extensive interactions — is not a safe option.

That said, always tell your healthcare provider about all medications, vitamins, and supplements you take before starting Lagevrio.

Tips for Managing Side Effects

Take Lagevrio with food if you experience nausea

Stay well hydrated if you have diarrhea

Avoid alcohol during treatment — it may worsen dizziness and impair your immune response

Complete the full 5-day course even if you feel better — stopping early risks treatment failure

For more information on interactions and what to tell your doctor, see our guide on Lagevrio drug interactions.

If you haven't filled your prescription yet, see our guide on how to find Lagevrio in stock near you.