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Ingredient guide

How long does valerian root take to work?

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

Valerian's marker compound peaks in the blood 1 to 2 hours after a dose, but one dose may not be enough. In a small sleep lab study, a single 600 mg dose made no measurable difference, while 14 nights shortened the time to reach deep sleep. In a 28-day trial, the gap over placebo grew after day 14.1,2

Key facts

  • Most valerian sleep studies tested repeated doses rather than a single night.3
  • A 2020 review suggests repeated use is needed before effects show.3
  • Valerenic acid levels after the same dose varied widely between people, unrelated to age or weight.1
  • NIH says there is no agreement on which compounds make valerian work.2

How fast it gets into the blood

In six healthy adults given a single 600 mg dose, valerenic acid, a compound used to identify valerian, reached its highest level 1 to 2 hours later in five of them.1

Valerenic acid stayed measurable in the blood for at least 5 hours after a 600 mg dose, and half of it was cleared in about 1.1 hours on average.1

Valerenic acid is a marker, not necessarily the compound that does the work. Its blood level shows when the root has been absorbed, not when an effect will start.1,2

One dose or several weeks

In a small sleep lab study of 16 people, a single 600 mg dose made no measurable difference. After 14 nights, NIH reports that 1 of 15 measures differed from placebo: people reached deep sleep sooner. In a 28-day trial of 121 people, the gap between valerian and placebo widened between day 14 and day 28.2,3

A 2020 review drew the same lesson from the wider research. Most studies tested repeated doses over 5 days to 8 weeks, and single doses of alcohol-based extracts did not change sleep quality.3

A 28-day trial comparing valerian with a prescription sedative checked sleep after 1, 2 and 4 weeks, and sleep quality scores rose in both groups over that time.4

For hot flashes

In the two hot flash trials, differences from placebo were measured after 4 and 8 weeks in one, and after 1 and 2 months in the other. In the second trial, severity differed at one month but frequency only at two.5,6

Stopping after long use

NCCIH reports that some people who stop suddenly after long daily use get withdrawal symptoms, such as anxiety, irritability, heart disturbances and trouble sleeping. If you have taken valerian daily for a long time, ask a doctor how to stop.7

Questions people ask

How long does valerian root stay in your system?

In a study of six adults, valerenic acid could be measured for at least 5 hours after a 600 mg dose, and half of it was gone in about 1.1 hours on average. The many other compounds in valerian were not measured.1

How long does valerian take to kick in?

Its marker compound peaks 1 to 2 hours after a dose, which is why it is usually taken 30 minutes to 2 hours before bed. But in several studies a single dose did little, and the effects that were seen came with repeated nightly use.1,3

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Sources

  1. Anderson GD, Elmer GW, Kantor ED, Templeton IE, Vitiello MV. Pharmacokinetics of valerenic acid after administration of valerian in healthy subjects. Phytother Res. 2005;19(9):801-803. Opened 2026-10-07.
  2. National Institutes of Health, Office of Dietary Supplements. Valerian: Fact Sheet for Health Professionals. Updated March 15, 2013. Opened 2026-10-07.
  3. Shinjyo N, Waddell G, Green J. Valerian Root in Treating Sleep Problems and Associated Disorders: A Systematic Review and Meta-Analysis. J Evid Based Integr Med. 2020;25:2515690X20967323. Opened 2026-10-07.
  4. Dorn M. Efficacy and tolerability of Baldrian versus oxazepam in non-organic and non-psychiatric insomniacs: a randomised, double-blind, clinical, comparative study. Forsch Komplementarmed Klass Naturheilkd. 2000;7(2):79-84. Article in German, English abstract. Opened 2026-10-07.
  5. Mirabi P, Mojab F. The effects of valerian root on hot flashes in menopausal women. Iran J Pharm Res. 2013;12(1):217-222. Opened 2026-10-07.
  6. Jenabi E, Shobeiri F, Hazavehei SMM, Roshanaei G. The effect of Valerian on the severity and frequency of hot flashes: A triple-blind randomized clinical trial. Women Health. 2018;58(3):297-304. Opened 2026-10-07.
  7. National Center for Complementary and Integrative Health. Valerian. Bethesda (MD): National Institutes of Health. Last updated May 2025. Opened 2026-10-07.

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