Valerian root side effects

Valerian root's most consistently reported side effect across trials is drowsiness, including next-day grogginess in some cases. Rare case reports describe liver injury, and, after long-term high-dose use is stopped abruptly, withdrawal symptoms including delirium — real but uncommon findings, not typical outcomes.

What shows up most often

Across a 2006 review of 16 placebo-controlled trials, 5 reported no adverse events at all, and the other 8 reported various mild side effects — but at rates similar between the valerian and placebo groups, with no statistically significant difference (PMID 17145239). A 2007 review of 37 studies described valerian as safe with only rare adverse events, even as it found no consistent sleep benefit over placebo (PMID 17517355). The most commonly named side effects across sources are dizziness, headache, and next-day grogginess or drowsiness (PMID 30000874).

Drowsiness and grogginess

Drowsiness is the side effect people ask about most, and it's also tied to the mechanism researchers think might explain any effect — valerenic acid, one of valerian's compounds, has been shown in lab studies to slow the breakdown of GABA, a calming brain chemical (PMID 10411208). In one small trial, drowsiness was reported more often at a 300 mg dose (12 of the group) than at 600 mg (4) or placebo (8) — not a clean dose-response pattern, but a sign that some grogginess is common regardless of amount (PMID 33086877). If you notice grogginess the next day, see when is the best time to take valerian root? for how trials timed their doses.

Liver: rare case reports

Two published case reports describe hepatotoxicity — liver injury — in people taking valerian (PMID 19138557, PMID 18431248). Both are single case reports, which means they can tell us this has happened, but not how often it happens across everyone who takes valerian. If you notice yellowing skin or eyes, unusually dark urine, itching, or pain under the right ribs, stop and see a doctor. More on who should be extra cautious in who should not take valerian root?

Stopping after long-term use

Two published case reports describe delirium — and in one case, cardiac complications — after people stopped valerian abruptly following months of daily, high-dose use (PMID 9820254, PMID 32576405). Both involved prolonged, high intake before a sudden stop, not a typical short-term pattern of use — but it's a reason to taper down gradually rather than quit suddenly if that describes how you've been taking it.

Vivid dreams: a common question, not a documented finding

Vivid dreams come up often in searches about valerian, but none of the trials we reviewed measured dream content or vividness as an outcome. That doesn't rule it out as something some people experience — it means there's no rate or mechanism from the research to report.

Questions people ask

Does valerian root make you sleepy?

Drowsiness is one of the more consistently reported effects across valerian trials, sometimes lasting into the next day. It's listed as a side effect in the research, not a guaranteed effect for everyone.

Why does valerian root make you sleepy?

The leading laboratory theory involves valerenic acid, one of valerian's compounds, which has been shown to slow the breakdown of GABA, a calming brain chemical. That's a mechanism identified in lab research, alongside drowsiness being one of the more commonly reported effects in human trials.

What are the side effects of valerian root?

Most commonly: dizziness, headache, and drowsiness or next-day grogginess. Less commonly, and documented only in individual case reports: liver injury, and delirium after abruptly stopping long-term, high-dose use.

Does valerian root have side effects?

Yes, though most trials describe it as generally well tolerated, with side effect rates similar to placebo in most studies. The rarer effects — liver injury, withdrawal delirium — come from individual case reports rather than controlled trials.

Can valerian root cause dizziness?

Yes — dizziness is one of the side effects listed in a national reference database on herbal supplements, alongside headache and grogginess, described as occurring occasionally.

Can you be allergic to valerian root?

General allergic reactions to any supplement ingredient are possible, valerian included. Stop taking it and see a doctor if you notice hives, swelling, or difficulty breathing.

Related reading: who should not take valerian root?, valerian root and medications: what to check, and how much valerian root should you take a day?