Can aciclovir cause nausea and dizziness?
Yes. Nausea is a known side effect of aciclovir, and dizziness can also occur. Both can happen when the medicine affects the gastrointestinal tract and the nervous system, or when drug levels rise due to higher doses or reduced kidney function.
When are nausea and dizziness more likely?
Nausea and dizziness are more likely if:
- You take aciclovir at a higher dose or more frequently than usual.
- You have kidney problems (aciclovir is cleared through the kidneys, so it can build up).
- You are older, dehydrated, or taking other medicines that also affect the kidneys or the nervous system.
- You are taking oral aciclovir and notice symptoms soon after starting or after a dose change.
What should you do if you feel nauseated or dizzy after taking aciclovir?
- Check timing: if symptoms start after doses, that strengthens the connection.
- Stay hydrated unless your clinician has restricted fluids.
- Contact a healthcare professional promptly for advice, especially if symptoms are new, worsening, or severe.
- Seek urgent care immediately if you have signs of a serious reaction, such as fainting, severe confusion, severe headache, trouble breathing, or swelling of the face/throat.
Could something else be causing it?
Yes. The infection being treated can also cause nausea, dizziness, and fatigue. But when symptoms line up with taking aciclovir or worsen after doses, aciclovir becomes a more likely contributor.
Are there alternatives if symptoms are troublesome?
Depending on why you’re taking aciclovir (cold sores, shingles, herpes infections, etc.) and your kidney function, clinicians may adjust the dose, switch to a different antiviral, or change the route (oral vs. topical). The right option depends on your diagnosis and medical history.
When to ask for medical review urgently (especially with dizziness)
Get urgent help if dizziness comes with any of the following:
- Severe drowsiness or confusion
- Trouble speaking, weakness on one side, or new neurologic symptoms
- Very low urine output or signs of dehydration
- Severe vomiting or inability to keep fluids down
Sources: none provided.