Quick answer

Headaches, dizziness, itching and stomach upset were the most common effects in valerian trials, but NIH's Office of Dietary Supplements says people taking placebo reported similar effects. NCCIH lists headache, stomach upset, mental dullness, excitability, uneasiness and vivid dreams. Ask your doctor if headaches follow valerian.^1,2

Key facts

Headaches, dizziness, itching and stomach upset were the most common effects reported in valerian trials, and similar effects were reported by people taking placebo.¹
NCCIH lists headache, stomach upset, mental dullness, excitability, uneasiness and vivid dreams among valerian's side effects.²
A systematic review of 60 studies reported no severe adverse events with valerian in people aged 7 to 80.³
In one small study, people felt sleepier the morning after a 900 mg dose, and in another a 600 mg dose had no clinically significant effect on alertness the next morning.¹
A minority of people felt agitated or restless instead of calm, and stopping suddenly after long use may cause withdrawal effects.^2,3

What do NIH sources list as side effects?

Two NIH sources name headache. NCCIH includes it in its list of valerian's side effects. The Office of Dietary Supplements goes a step further and tells readers how to interpret it: headache appeared in trials, but so did similar effects in people given placebo.^1,2

Side effects of valerian include headache, stomach upset, mental dullness, excitability, uneasiness and vivid dreams.²

In clinical trials, headaches, dizziness, itching and stomach upset were the most common effects reported, but people taking placebo reported similar effects.¹

Does that mean valerian causes the headaches?

Not necessarily. When headache turns up equally in the valerian and placebo groups of a trial, the trial cannot tell whether the herb caused it. That is the position NIH describes. It does not say valerian never causes headache, only that trials have not shown it to do so more often than a placebo.¹

The 2020 systematic review of 60 studies reached a related conclusion about serious problems: no severe adverse events were associated with valerian in people aged 7 to 80. The review also pointed to variable extract quality as a possible reason studies disagree, which matters because NIH says the composition of supplements may vary considerably between production lots.^1,3

What about drowsiness, dizziness and vivid dreams?

NIH's fact sheet lists dizziness among the most common trial effects, and one small study found people sleepier the morning after a 900 mg dose. Another study found that 600 mg had no clinically significant effect on reaction time, alertness or concentration the next morning. NCCIH lists vivid dreams among valerian's side effects.^1,2

In studies of healthy adults and older volunteers, single doses of standardized extracts from 100 to 1,600 mg did not impair thinking or reaction speed.³

A minority of people in studies felt agitated or restless rather than calm, and in one study a higher dose of the same product raised anxiety while a lower dose did not.³

What happens with long use, or when stopping?

NCCIH says that stopping valerian suddenly after long-term use may cause withdrawal effects, including anxiety, irritability and, rarely, hallucinations. It also says that in very rare cases liver injury has been reported, most often with other herbs, and that valerian's long-term effect on the liver is unknown.²

In very rare cases, liver injury has been reported in people taking valerian, most often in combination with other herbs. NIH's LiverTox database links valerian to rare instances of liver injury, and its long-term effect on the liver is unknown.^2,4

Who should ask a doctor?

Anyone with frequent or severe headaches after starting valerian should ask a doctor whether the supplement could be involved.
Anyone taking sedatives, sleeping pills or other drowsy-making medicines should ask a pharmacist, because NIH says valerian might add to their effects.¹
Anyone who has used valerian daily for a long time and wants to stop should ask first, because of the withdrawal effects NCCIH describes.²
Anyone with liver disease should ask before using it, because liver injury has been reported in rare cases.²

Questions people ask

Does valerian cause vivid dreams or nightmares?

NCCIH lists vivid dreams among valerian's side effects. The sources we read do not name nightmares. Ask your doctor if your dreams become disturbing.²

Does valerian cause dizziness or drowsiness?

NIH lists dizziness among the most common effects in trials, similar to placebo, and reports that people felt sleepier the morning after a 900 mg dose in one study.¹

Does valerian cause constipation or diarrhea?

NIH lists gastrointestinal disturbances and NCCIH lists stomach upset, and neither names constipation or diarrhea specifically. Ask your doctor if a bowel change follows valerian.^1,2

Does valerian cause dementia?

None of the sources we read report that valerian causes dementia, which is not a finding either way. The sources do not describe long-term effects beyond a few weeks.²

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.