Valerian root is one of the most common natural sleep aids available.

It’s used to improve poor sleep patterns, alleviate anxiety, ease menopausal symptoms, and promote relaxation. Used medicinally for thousands of years, it’s commonly taken as a capsule, liquid extract, or tea.

This supplement comes from the herb Valeriana officinalis, which is native to Asia and Europe but also grows in other countries like the United States.

One review of 11 herbal medicines concluded that valerian root was the most promising herbal medicine for sleep and insomnia (1).

All the same, reports of its effectiveness are mixed and largely based on anecdotal evidence. What’s more, some people report side effects, which appear to vary significantly between individuals (1, 2, 3, 4).

Here are 4 possible side effects of valerian root.

1. Vivid dreams

One of the most frequently reported side effects of valerian root is vivid dreams.

One study examined the side effects of valerian and kava, another herb, taken for insomnia. Researchers gave 24 people 4 ounces (120 mg) of kava daily for 6 weeks, followed by a 2-week break, then 20 ounces (600 mg) of valerian daily for 6 weeks (6).

While the majority of participants did not experience side effects, 16% experienced vivid dreams during the valerian treatment.

Valerian may cause vivid dreams because it contains essential oil and compounds called iridoid glycosides. These compounds stimulate opioid receptors and serotonin production in your brain, producing relaxing and anti-depressive effects (6).

Some researchers also believe that valerian boosts the brain chemical gamma aminobutyric acid (GABA), which has a calming effect on your body (7).

Overall, these sedative properties may promote deeper sleep patterns that could lead to vivid dreams.

For this reason, valerian root is not typically recommended for people who are prone to unpleasant dreams, as it could cause nightmares.

SUMMARY

Valerian root is known to have sedative effects, which is one reason it’s used for insomnia. However, using valerian may lead to vivid dreams or even nightmares in some people.

2. Heart palpitations

Heart palpitations feel like a rapid or fluttering heartbeat.

Though typically harmless, they can be worrisome if you’re not used to them. Heart palpitations may be triggered by stress, medication, exercise, or a medical condition.

Historical reports suggest that valerian root was used to treat heart palpitations as far back as the 16th century.

Ironically, some people have experienced heart palpitations as a side effect of using or discontinuing valerian root. However, these reports are anecdotal and not based on research (8).

As such, human studies are needed to verify its potential effects.

SUMMARY

Some people claim that valerian root causes heart palpitations or increased heart rate, but the evidence for this is mostly anecdotal.

3. Dry mouth and upset stomach

Valerian root may cause mild to moderate mouth and digestive effects.

Some people report an increase in bowel activity after using it. Fittingly, valerian has been used for centuries in Europe to treat digestive problems like constipation (9).

All the same, these laxative effects could cause undesirable symptoms like diarrhea or upset stomach.

A 28-day study in 391 people given various herbs for sleep treatment showed that 18% of those who took valerian root experienced an increase in diarrhea, compared with only 8% of those in the placebo group (2, 4).

Other people have reported developing dry mouth after taking valerian root, but this has not been extensively studied.

SUMMARY

Valerian root appears to have a laxative effect, which may lead to diarrhea or upset stomach. Some people also report dry mouth.

4. Headaches and mental fogginess

Although valerian root has historically been used to alleviate headaches, some people report an increase in headaches and mental fogginess after using the herb (8, 10).

Most of these side effects seem to result from long-term or high-dose usage of this herb. All the same, symptoms may include not only more headaches but also other brain-related issues, such as excitability and uneasiness (10).

Some people also report feeling more sluggish the morning after taking valerian root, especially at high doses — even if it helped them sleep better.

As such, if you experience any of these symptoms, you may want to lower your dosage.

Keep in mind that these side effects are based on anecdotal evidence. Therefore, more rigorous, scientific studies are needed.

SUMMARY

Valerian root may cause mental sluggishness and headaches, as well as other symptoms like uneasiness and excitability. These issues seem mostly related to high-dose or long-term usage of this herb.

Potential interactions

As with other herbs, caution should be taken when using valerian root alongside other substances and medications.

Though serious side effects appear to be rare, some sources report that valerian root may interact with the following (10, 11, 12, 13):

  • alcohol
  • antidepressants
  • sedatives, such as anticonvulsants, benzodiazepines, and sleep aids
  • narcotics
  • statins (cholesterol-lowering medications)
  • some antifungal drugs
  • antihistamines
  • St. John’s wort

Valerian root should not be taken in high doses or in tandem with substances used for similar reasons, such as sedatives or sleep aids.

Using this herb with some of these substances may cause excessive sleepiness or worsen depression. Valerian root may also slow the breakdown of drugs by your liver, causing them to accumulate in your body or be less effective (10, 12, 13).

What’s more, young children and pregnant or breastfeeding women should avoid valerian root due to a lack of safety information (14, 15).

Keep in mind that this herb is considered a dietary supplement and not regulated by the Food and Drug Administration (FDA). Thus, it’s best to look for products that have been independently tested for purity by organizations like NSF International or ConsumerLab.

Always remember that valerian should not replace prescription medications. If you’re unsure how to use valerian root, seek advice from a medical professional.

SUMMARY

You shouldn’t take valerian with other substances or drugs that have similar sedative effects, as this combination could cause exhaustion. It’s best to speak to a health professional regarding potential interactions.

Proper dosage and excessive intake

Research is mixed when it comes to the best dosage of valerian root. Many studies are small and have used widely varying amounts, making it difficult to determine the optimal intake (2).

Nonetheless, the general recommended dose of valerian for sleep trouble is 300–600 mg taken 30–120 minutes before bedtime. To make a tea instead, steep 2–3 grams of dried valerian root in hot water (16).

While this herb is usually tolerated well, there are a few reports of possible valerian toxicity linked to more severe symptoms, including headaches, liver toxicity, chest tightness, abdominal pain, and tremors (10, 16, 17, 18).

As these reports focus on individuals, more comprehensive population studies are needed.

There’s no significant evidence that taking large amounts of valerian root is dangerous.

SUMMARY

Although a few case reports point to side effects from high doses of valerian root, no scientific evidence suggests that high doses are harmful. Still, more controlled, human studies are necessary.

The bottom line

Valerian root is a popular sleep aid that’s widely considered safe.

Still, some people have reported several minor side effects, such as vivid dreams, heart palpitations, dry mouth, digestive upset, headaches, and mental fogginess.

If you’re experiencing any side effects that you think could be related to valerian root, consider reducing your dosage.

Moreover, if you’re uncertain about how to use this herb, speak to your healthcare provider for more guidance.