Can You Take Valerian and Ashwagandha Together?

No well-designed human trial has specifically tested the safety or effectiveness of taking valerian and ashwagandha at the same time, so there is no firm clinical answer. That said, the two herbs work through different biological pathways, and a recent review of medicinal plants for anxiety-related insomnia identified both as among the most promising botanicals in the category, suggesting their mechanisms are at least complementary in theory.¹ The real question is less whether the combination “works” and more whether stacking two herbs with sedative and hormonal effects creates risks you should know about before you try.

How Each Herb Works in the Body

Valerian root acts primarily on the brain’s calming neurotransmitter system. Its active compounds, particularly valerenic acid, appear to increase the availability of GABA by slowing its breakdown and by binding directly to the same receptors that drugs like benzodiazepines target.² This is why valerian is most commonly used as a sleep aid and mild sedative. It promotes drowsiness by dampening nervous-system activity, much like a milder version of a prescription sleep medication.

Ashwagandha operates through a different set of pathways. A systematic review and meta-analysis found that it produces measurable reductions in stress, anxiety, and serum cortisol levels, likely driven by its active compounds called withanolides.³ Rather than directly sedating you, ashwagandha appears to buffer the body’s stress response, lowering the hormonal cascade that keeps you wired. It also has effects on the thyroid and immune system that valerian does not share, which matters for safety.

Because one herb targets GABA and the other targets cortisol and stress hormones, the combination is sometimes marketed as hitting relaxation from two different angles. That framing is not unreasonable on paper, but it also means you are introducing two separate sets of biological effects into your body at once, each with its own side-effect profile.

The Limited Evidence for the Combination

Only one published study has directly tested a product containing both herbs. Researchers formulated a nutraceutical gummy combining ashwagandha and valerian and tested it in an animal model of depression. Animals given the gummy showed roughly a 40 percent reduction in immobility time and a 35 percent increase in climbing activity compared to controls, which researchers interpreted as a robust antidepressant-like effect.⁴ That is an animal study using a single behavioral test, so it tells us almost nothing about what the combination does in people, at what dose, or how safe it is over weeks or months.

Beyond that, the evidence is indirect. A review of medicinal plants for anxiety-related insomnia concluded that valerian, passionflower, and ashwagandha were the three most promising individual botanicals, and that valerian combined with hops or passionflower gave the best clinical results in human trials.¹ The fact that valerian-plus-ashwagandha was not highlighted as a tested combination is telling. Researchers have studied valerian paired with other herbs (hops is the most common partner in clinical trials), but the valerian-ashwagandha pairing has not received that kind of attention.

This means you are essentially running an uncontrolled experiment if you take both. That does not automatically make it dangerous, but it does mean any claims about the combination being “safe and effective” are getting ahead of the science.

Sedation and Drug Interactions

The most predictable concern with combining these two herbs is excessive sedation. Valerian’s GABA-boosting effect is pharmacologically similar to the action of benzodiazepines and other sedatives, and a review of valerian’s interaction profile noted that the most plausible drug interactions involve substances that influence alertness, such as codeine, certain antidepressants, and benzodiazepines.⁵ Ashwagandha is not a direct sedative, but by lowering cortisol and buffering the stress response, it can increase drowsiness, especially at higher doses or later in the day.

If you are already taking a prescription sleep aid, an anti-anxiety medication, an antidepressant, or anything else that crosses into sedation territory, adding both valerian and ashwagandha on top could compound the effect. The same review noted that the in vitro evidence behind valerian’s predicted interactions with benzodiazepines is still inconclusive and needs replication, so the risk is more theoretical than proven.⁵ Still, “theoretical but pharmacologically plausible” is a reason for caution, not a green light.

A broader review of herbal supplements and sleep found that while supplements like valerian are generally considered safe, they are not without risks, including potential interactions with prescription medications.⁶ Ashwagandha brings its own interaction concerns, with a critical review identifying populations at increased risk of adverse reactions and interactions with prescribed drugs.⁷ When you stack both herbs together, you are stacking both sets of interaction risks.

Liver Safety Is the Quiet Concern

This is probably the most underappreciated risk of combining the two. Both valerian and ashwagandha have been independently linked to liver injury in case reports, and the liver is the organ responsible for processing both of them.

For valerian, a case report documented a patient whose liver enzymes rose during valerian use and returned to normal within three months of stopping it.⁸ Lab research has also shown that high concentrations of valerian can cause cell death in cultured human liver cells, though the doses involved were orders of magnitude higher than what a person would normally take.⁹

For ashwagandha, the evidence of liver harm is more developed and more concerning. A case series from India documented 23 patients with liver injury linked to ashwagandha use between 2019 and 2022. Among them, eight were taking single-ingredient ashwagandha formulations. Five already had underlying chronic liver disease, and three of those developed acute-on-chronic liver failure and died.¹⁰ Another review compiled reported cases and described two new ones in which otherwise healthy adults in their thirties developed symptoms like nausea, itching, and dark urine after weeks or months of regular ashwagandha use. Both cases scored “probable” on the standard causality assessment tool for drug-induced liver injury, and both improved after stopping the supplement.¹¹ At least one case in the published literature progressed to the point of requiring a liver transplant.¹¹ An additional case report described a patient who developed acute hepatitis after ashwagandha use, with lab results showing a pattern consistent with cholestatic liver damage and severe jaundice.¹²

These are rare events relative to the number of people taking ashwagandha, and case reports cannot prove causation by themselves. But the pattern is consistent enough that researchers have flagged it as a genuine safety signal. When you take two herbs that are each individually capable of stressing the liver, even at low individual risk, the combined load is worth thinking about. If you have any existing liver condition, drink heavily, or take other medications processed by the liver, this concern gets substantially more serious.

Ashwagandha and Your Thyroid

This is a risk that valerian does not share, but it matters for anyone planning to stack these supplements. Ashwagandha appears to stimulate thyroid hormone production. A double-blind, placebo-controlled trial in people with subclinical hypothyroidism found that eight weeks of ashwagandha significantly improved TSH, T3, and T4 levels compared to placebo.¹³ For someone with an underactive thyroid, that sounds like good news, but it can tip the balance dangerously in the wrong direction.

A case report described a 73-year-old woman who had been self-treating her hypothyroidism with ashwagandha for two years and developed thyrotoxicosis, presenting with a racing heart and dangerously low TSH levels. Her symptoms resolved after she stopped taking the supplement.¹⁴ If you are on thyroid medication, adding ashwagandha could push your levels out of the range your doctor has carefully calibrated. This has nothing to do with valerian, but if you are building a nightly supplement stack, it is a risk that comes along for the ride with ashwagandha.

Autoimmune Conditions and Immune Stimulation

Ashwagandha is widely marketed as an “immune booster,” and the label is not entirely wrong. Animal studies have shown it can suppress autoreactive immune cells and inflammatory signaling in models of rheumatoid arthritis and lupus, though clinical evidence in humans with autoimmune conditions is thin.¹⁵ The problem is that “immune modulation” can cut both ways.

A systematic scoping review identified ashwagandha among 15 herbs with robust evidence of proinflammatory activity, including activation of pathways that ramp up inflammatory signaling molecules like IL-6 and TNF-α. The review specifically flagged these herbs as potentially capable of flaring autoimmune skin diseases.¹⁶ If you have lupus, multiple sclerosis, rheumatoid arthritis, or another autoimmune condition, adding ashwagandha could theoretically stimulate the exact immune activity your treatments are trying to suppress. Valerian does not carry this specific concern, but pairing it with ashwagandha means you are still exposed to it.

Before Surgery, Stop Both

If you have an upcoming surgical procedure, both herbs need to be on your discontinuation list. The American Society of Anesthesiologists and the American Association of Nurse Anesthetists recommend stopping herbal medications one to two weeks before elective surgery. The reasons span multiple body systems: herbal products can interact with anesthetic drugs, affect blood clotting, alter blood pressure, cause excessive sedation, and interfere with liver metabolism of surgical medications.⁶ Valerian’s sedative properties and ashwagandha’s hormonal effects both fall into categories that anesthesiologists worry about.

There is also a withdrawal consideration with valerian specifically. A case report in a major medical journal documented serious cardiac complications and delirium associated with abrupt valerian withdrawal in a patient who had been using it long-term, with the withdrawal profile resembling what can happen with benzodiazepines.¹⁷ If you have been taking valerian regularly, this is not something to stop cold-turkey the night before surgery. Taper off gradually and give your doctor the full picture of what you have been taking.

Supplement Quality Adds Another Variable

Even if the herbs themselves were perfectly safe at standard doses, what is actually in the bottle matters enormously. Herbal dietary supplements, including popular adaptogens like ashwagandha, face inconsistent regulatory standards and carry a real risk of heavy metal contamination.¹⁸ Because supplements are not required to prove safety or efficacy before reaching shelves in most countries, two bottles of “ashwagandha 600 mg” from different brands can contain very different amounts of the active withanolide compounds.

Research on ashwagandha bioavailability illustrates how much formulation matters. A study comparing different ashwagandha extracts found that a novel formulation at just 125 mg delivered over twice the bioavailability of total withanolides compared to a standard 600 mg extract.¹⁹ When dose-normalized for withanolide content, the differences were staggering. This means that what you think you are taking and what your body actually absorbs can be wildly different depending on the product. When you are combining two herbs, this uncertainty doubles.

If you do decide to take both, choosing products from brands that use third-party testing and standardize their extracts to known concentrations of active compounds is one of the few practical steps you can take to reduce unpredictability. Look for certificates of analysis from independent labs, and be skeptical of products that do not specify the concentration of valerenic acid (for valerian) or withanolides (for ashwagandha) on the label.

A Practical Framework if You Decide to Try Both

Given the gaps in the research, anyone considering this combination is making a judgment call rather than following established medical guidance. A few principles can make that judgment call less risky:

• Start one at a time: If you introduce both herbs simultaneously and develop a side effect, you will not know which one caused it. Start with one herb for at least two to three weeks before adding the second.
• Use conservative doses: Since no one has established what a safe combined dose looks like, beginning at the lower end of each herb’s recommended range reduces the chance of compounding sedation or liver stress.
• Watch for warning signs: Unusual fatigue, yellowing of the eyes or skin, dark urine, persistent nausea, or unexplained itching are all signals that your liver may be struggling. Stop both supplements and see a doctor.
• Disclose to your doctor: Many people do not mention supplements during medical visits, which leaves doctors unable to catch interactions or interpret lab results correctly. This is especially true if you are on thyroid medication, immunosuppressants, sedatives, or blood-pressure drugs.
• Avoid long-term unmonitored use: Most clinical trials of either herb run eight to twelve weeks. Extending use beyond that without periodic check-ins is venturing further past where the evidence reaches.

Why “Natural” Does Not Mean “Freely Combinable”

The cultural assumption behind many herbal stacking questions is that natural products are inherently gentle and that combining them is like mixing herbal teas. The case reports and reviews covered here paint a more complicated picture. Ashwagandha can shift thyroid hormones enough to trigger a cardiac arrhythmia in a vulnerable person.¹⁴ Valerian acts on the same receptor system as prescription tranquilizers, and abrupt withdrawal after long-term use has been associated with serious cardiac events.¹⁷ These are not synthetic chemicals invented in a lab; they are biologically active compounds that happen to come from plants. The distinction between “natural” and “pharmaceutical” is a marketing category, not a pharmacological one.

None of this means the combination is guaranteed to harm you. For a healthy adult without liver issues, thyroid problems, autoimmune disease, or concurrent medication use, taking standard doses of both herbs for a few weeks is unlikely to cause a dramatic adverse event. But “unlikely to cause a dramatic adverse event in the short term for healthy people” is a lower bar than most supplement companies would like you to think about. The honest answer is that no one has studied this pairing carefully enough to say much more than that.