Studied doses range from 400 to 900 milligrams of an aqueous or aqueous-ethanolic extract (corresponding to 1.5 to 3 grams of herb), taken 30 to 60 minutes before going to bed. Valerian has historically been used in the form of a tea (1.5 to 3 grams root steeped for five to 10 minutes in 150 milliliters boiling water), although this formulation has not been studied. Doses of 300-1,800 milligrams of valerian have also been taken by mouth in capsule form.
There is not enough scientific evidence to recommend the use of valerian in children.
People with allergies to plants in the Valerianaceae family may be allergic to valerian.
Studies report that valerian is generally well tolerated for up to four to six weeks in recommended doses. Valerian has occasionally been reported to cause headache, excitability, stomach upset, uneasiness, dizziness, unsteadiness (ataxia), and low body temperature (hypothermia). Chronic use (longer than two to four months) may result in insomnia. Slight reductions in concentration or complicated thinking may occur for a few hours after taking valerian. Use caution if driving or operating heavy machinery. Some research suggests that valerian may not cause sedation.
A drug "hangover" effect has been reported in people taking high doses of valerian extracts. "Valerian withdrawal" may occur if you stop using valerian suddenly after chronic high-dose use, including confusion (delirium) and rapid heartbeat. These symptoms may improve with the use of benzodiazepines such as lorazepam (Ativan®). Although unknown, valerian may have similar brain activity as benzodiazepines (which are commonly used to treat anxiety and insomnia), through effects on the brain chemical gamma-amino-butyric-acid (GABA).
Valerian has been on the U.S. Food and Drug Administration's (FDA's) GRAS (Generally Regarded as Safe) list, and no deaths due to overdose are currently available.
Liver toxicity has been associated with some multi-herb preparations that include valerian. However, the contribution of valerian itself is not clear due to the potential liver toxicity of other included ingredients and the possibility of contamination with unlisted herbs.
Because there is limited human safety data, valerian use during pregnancy and breastfeeding is not recommended. There are theoretical concerns over the adverse effects of chemical components that are toxic in laboratory studies.