Valerian root is a plant-based supplement made from the roots of Valeriana officinalis, a flowering plant native to Europe, Asia, and North America. It has been used as a sleep aid for over 2,000 years, making it one of the oldest herbal remedies still in widespread use today. Despite its long history, modern evidence for its effectiveness is surprisingly mixed.
A Plant With Ancient Roots
The Greek physician Hippocrates prescribed valerian for sleep problems around 400 BCE. Dioscorides, another Greek physician in the first century CE, did the same. Galen, who served as personal physician to the Roman emperor Marcus Aurelius, specifically recommended it for insomnia around 170 CE. The plant has remained a go-to herbal remedy in Europe and beyond ever since.
The medicinal part is the root and underground stem (rhizome), not the flowers or leaves. These are dried and processed into capsules, tinctures, teas, or standardized extracts. If you’ve ever opened a bottle of valerian capsules, you’ll recognize the distinctly pungent, earthy smell, sometimes compared to old socks. That smell comes from the volatile oils concentrated in the root.
How It Works in the Brain
Valerian root contains dozens of active compounds, but the one that gets the most scientific attention is valerenic acid. This compound acts on GABA receptors in the brain. GABA is the main chemical messenger that calms nerve activity, and it’s the same system targeted by prescription sleep and anxiety medications. Valerenic acid doesn’t work the same way those drugs do. Instead, it acts as an “allosteric modulator,” meaning it fine-tunes how GABA receptors respond rather than activating them directly. The effect is subtler.
Beyond valerenic acid, valerian root contains other sesquiterpenes, iridoids called valepotriates, and various volatile oils. Researchers believe the sedative effect likely comes from multiple compounds working together rather than any single ingredient, which is one reason the supplement is difficult to study consistently.
What the Evidence Says About Sleep
This is where valerian’s reputation and the research diverge. A 2024 umbrella review that analyzed all available evidence concluded there is no strong evidence that valerian effectively treats insomnia when measured objectively. That means in sleep lab studies tracking brain waves, time to fall asleep, and total sleep duration, valerian didn’t consistently outperform a placebo.
However, the same review found that people taking valerian often reported feeling like their sleep quality improved. This subjective benefit is real and consistent across multiple trials, even when the objective measurements don’t budge. Whether that reflects a genuine mild effect, a strong placebo response, or something the instruments can’t capture is still debated. For someone simply hoping to feel more rested, that distinction may matter less than it sounds.
Clinical trials have used doses ranging from 300 mg to 1,600 mg of valerian root extract, with most standardized to contain about 0.8% valerenic acid. The most commonly studied dose is 400 to 600 mg taken 30 minutes to two hours before bed. Some studies used a single dose while others gave valerian for two weeks or longer, and some evidence suggests it may work better with continued use rather than as a one-night fix.
Capsules, Teas, and Tinctures
Not all valerian products deliver the same amount of active compounds. Standardized extract capsules are the most consistent, typically listing the valerenic acid content on the label (often around 0.8%, or roughly 5 to 11 mg of valerenic acid per dose depending on the product). These are what clinical trials have primarily used.
Valerian tea, made by steeping dried root in hot water, contains lower and more variable amounts of the active compounds. Tinctures (alcohol-based extracts) fall somewhere in between. If consistency matters to you, capsules standardized for valerenic acid content are the most reliable option. The volatile oils that contribute to valerian’s effects are also partly lost in tea preparation, since some evaporate with the steam.
Side Effects and Safety
Valerian has a good safety profile overall. The most commonly reported side effects are mild: drowsiness, dizziness, and occasionally headache or digestive upset. Some people experience withdrawal symptoms after stopping long-term use, similar to what can happen with other supplements that affect the GABA system.
Liver injury has been linked to valerian in a small number of published cases, but it is considered a very rare cause. Most reported cases involved valerian combined with other herbal products like skullcap or black cohosh, making it difficult to pin the damage on valerian alone. When liver problems did occur, they typically appeared 3 to 12 weeks after starting use and resolved within 2 to 4 months of stopping. No convincing case of acute liver failure from valerian alone has been published.
Drug Interactions
Because valerian affects the GABA system, there’s a logical concern about combining it with alcohol, sedatives, or other substances that slow brain activity. In practice, though, research has found the interaction potential to be low. Studies in both animals and humans have not confirmed clinically meaningful interactions, and valerian does not appear to significantly affect the liver enzymes responsible for processing most common medications.
That said, the theoretical risk of additive drowsiness still applies. If you’re taking anything that makes you sleepy, layering valerian on top could amplify that effect even if formal studies haven’t flagged a dangerous interaction.
Regulatory Status
In the United States, valerian is sold as a dietary supplement, not a medication. This means it doesn’t go through the same approval process as prescription or over-the-counter drugs, and manufacturers are responsible for their own quality control. In Europe, valerian has a more established regulatory framework, with some countries approving it as a traditional herbal medicine for mild sleep disturbances. The practical difference is that European products are more likely to meet standardized potency requirements, while U.S. products can vary significantly from one brand to another.
If you decide to try valerian, choosing a product from a manufacturer that uses third-party testing can help ensure you’re getting what the label claims. Look for a standardized valerenic acid content, and expect to give it at least a couple of weeks before judging whether it helps.