Can you take ashwagandha and L-theanine together?

Reviewed and updated: 22 October 2026

Yes, most healthy adults can take ashwagandha and L-theanine together, and they are often paired precisely because they come from such different places: one is an ancient Ayurvedic root, the other an amino acid from the tea leaf. There is no known clash between the two, so the real questions are how much, when, and whether anything else you take calls for a word with your pharmacist first.

This is one of the most common combinations I see people asking about, so here is everything I would want a friend to know before they try it.

Can you take ashwagandha and L-theanine together? The quick answer

• What it is: a standardised ashwagandha root extract alongside L-theanine, the amino acid found naturally in green and black tea.
• Who it suits: healthy adults building a steady daily routine who would rather take both in one capsule.
• Do they clash? They are not known to interact with each other, and they are commonly formulated together.
• Typical amounts: studies tend to use around 300 to 600 mg of standardised ashwagandha root extract a day and 100 to 200 mg of L-theanine.
• The key caution: ashwagandha is not for pregnancy or breastfeeding, and needs a check first if you take thyroid, sedative, blood pressure or immune-suppressing medicines.

A quiet half hour on the sofa with a cup of green tea. My favourite part of the afternoon. Illustrative image

Ashwagandha: an Ayurvedic root with a long story

Ashwagandha (Withania somnifera) is a small shrub whose root has been used in Ayurveda for well over two thousand years. Its Sanskrit name roughly means "smell of the horse", a nod to the root's earthy aroma and to the strength it was traditionally associated with. In traditional practice it was reached for during demanding, tiring periods and was valued as a root to help people feel calm and steady.

Today it is grouped with the adaptogens, a traditional term for plants used to help the body cope with everyday demands. The interesting compounds in the root are a family of molecules called withanolides, and how much of them an extract reliably carries is the clearest marker of quality. KSM-66, the extract we use, is made from the root only and standardised to a minimum of 5% withanolides, so every capsule is consistent. Our pillar guide on what KSM-66 ashwagandha is explains why that standardisation matters.

What the research has explored

Researchers have looked at standardised ashwagandha root extracts in a number of placebo-controlled trials, usually in healthy adults who describe themselves as stressed. A 60-day study by Lopresti and colleagues measured questionnaire scores, morning cortisol and other hormone markers, and a 90-day study by Gopukumar and colleagues looked at memory and attention tests alongside wellbeing questionnaires. The findings are encouraging in direction, but the trials are small, short and use different extracts, so I see them as interesting science about the root rather than a promise about how any one person will feel.

L-theanine: the quiet amino acid in your cup of tea

L-theanine is a non-protein amino acid made by the tea plant, Camellia sinensis. It is part of why a cup of tea has its particular character, and tea drinkers in China and Japan have enjoyed it for centuries without knowing its name. Its chemistry was only properly described in the twentieth century.

It is absorbed quickly and, according to the research summarised by Vuong and colleagues, reaches the brain within roughly half an hour to two hours. Most human studies have used amounts of around 100 to 200 mg. In one placebo-controlled crossover trial, White and colleagues gave healthy adults an L-theanine based drink before a demanding multitasking test and recorded how they rated their experience, their salivary cortisol and their brain-wave activity. It is a nice piece of science, and it helps explain why L-theanine is so often described as calming without being sedating.

Why people pair them

The logic is about timescale. L-theanine is the here-and-now ingredient: in studies its effects on brain activity show up within an hour or two and then fade. Ashwagandha is the slow, steady one: the trials that report anything usually run for six to eight weeks of daily use. Putting a quick amino acid alongside a root that is judged over weeks is why so many formulas, ours included, combine them.

There is a third ingredient worth knowing about too. We add vitamin B6, because B6 is where recognised nutrient functions come in: vitamin B6 contributes to normal psychological function, to the normal functioning of the nervous system and to the reduction of tiredness and fatigue.

Our pick for this guide

Want ashwagandha and L-theanine in one simple capsule?

KSM-66 full-spectrum ashwagandha root extract, standardised to a minimum of 5% withanolides, with L-theanine and vitamin B6. Vitamin B6 contributes to normal psychological function. A food supplement, not a replacement for medical advice.

From £11.99 · 60 vegan capsules

Shop Ashwagandha KSM-66 →

How much of each to take

There is no official combined dose, because these are food supplements rather than medicines, but the research points to sensible ranges:

• Ashwagandha: most trials use around 300 to 600 mg of a standardised root extract a day, taken once or split into two.
• L-theanine: 100 to 200 mg is the range most studies have used.
• Standardisation beats milligrams: 300 mg of a root extract standardised to 5% withanolides is a very different thing from 300 mg of plain root powder, so always check the withanolide percentage on the label.

Women often ask whether they need less. The honest answer is that the trials are not split that way, and our guide on how much ashwagandha per day for females walks through what the studies actually used.

When to take them

There is no single right time. Some people like the pair in the evening as part of winding down at the end of the day; others prefer the morning because L-theanine is not a sedative. Because ashwagandha is judged over weeks, the habit matters far more than the hour, so pick the time you will actually stick to. Our guide on when to take ashwagandha goes through the options in more detail.

With or without food?

Either is fine for most people. If ashwagandha ever feels unsettling on an empty stomach, take it with a meal or a snack.

Does the combination make you drowsy?

Neither ingredient behaves like a sleeping tablet. L-theanine in particular is usually described in the research as relaxing without drowsiness. That said, everyone is different, so when you first start, see how you respond before driving or doing anything that needs your full attention, and move your dose later in the day if you prefer.

Ashwagandha root, a little root powder and a cup of green tea. The two traditions this pairing comes from. Illustrative image

Can you add magnesium?

Many people add magnesium to this routine and there is no known problem doing so for most healthy adults. Unlike the root and the amino acid, magnesium is a mineral with recognised nutrient functions: magnesium contributes to normal psychological function, to the normal functioning of the nervous system and to the reduction of tiredness and fatigue. We look at that pairing in our guide to the best combinations with ashwagandha.

How long before you notice anything?

• L-theanine is acute. In studies, its effects show up within about an hour of a single dose and then wear off.
• Ashwagandha is cumulative. Trials almost always run daily for six to eight weeks, so give it at least four to six weeks of consistent use before you judge how it fits your routine.

Choosing a good combined product

• Look for a named, root-only extract with a stated withanolide percentage.
• Check that the L-theanine amount is printed in milligrams, not hidden in a blend.
• A sensible daily serving of one or two capsules that reaches study-level amounts.
• Recognised manufacturing standards. Ours is formulated in the UK and tested for purity and heavy metals at our GMP-certified facility.

A few cautions worth knowing

Most healthy adults tolerate this pairing well, but it is not for everyone. Please speak to your GP or pharmacist first if any of these apply:

• Pregnancy or breastfeeding: ashwagandha is not recommended, so avoid the combination.
• Thyroid medication or a thyroid condition: ashwagandha may influence thyroid hormone measures.
• Sedatives, sleep medicines or anti-anxiety medicines: check before combining with anything that has a similar calming effect.
• Blood pressure medication: both ingredients have been linked with modest blood pressure changes in some studies.
• Autoimmune conditions or immune-suppressing medicines: get tailored advice first.
• Liver: rare cases of liver problems have been reported with ashwagandha products, so stop and see your GP if you notice unusual tiredness, dark urine or yellowing of the skin or eyes.

Our full guide to ashwagandha safety and considerations covers each of these in more depth, and the supplement guides hub brings all of our ingredient guides together.

Frequently asked questions

Is it safe to take ashwagandha and L-theanine together?

For most healthy adults, yes. The two are not known to interact with each other and are commonly combined. Avoid the pairing in pregnancy and breastfeeding, and check with a pharmacist or GP first if you take thyroid, sedative, blood pressure or immune-suppressing medicines.

How much ashwagandha and L-theanine should I take together?

Studies typically use around 300 to 600 mg of a standardised ashwagandha root extract a day and 100 to 200 mg of L-theanine. Follow the serving on your product label and do not exceed it.

Should I take ashwagandha and L-theanine in the morning or at night?

Either works. Many people take the pair in the evening as part of winding down, while others prefer the morning because L-theanine is not a sedative. Consistency matters more than the exact time.

Will ashwagandha and L-theanine make me sleepy?

Neither is a sedative, and L-theanine is generally described as relaxing without drowsiness. Responses vary, so see how you feel before driving when you first start.

How long does it take for ashwagandha and L-theanine to work?

L-theanine acts within about an hour in studies, while ashwagandha trials usually run for six to eight weeks, so give a combined product at least four to six weeks of daily use.

Our pick for this guide

Ready to try ashwagandha with L-theanine and B6?

KSM-66 full-spectrum ashwagandha root extract, standardised to a minimum of 5% withanolides, with L-theanine and vitamin B6. Vitamin B6 contributes to normal psychological function. A food supplement, not a replacement for medical advice.

From £11.99 · 60 vegan capsules

Shop Ashwagandha KSM-66 →

Sources

• Lopresti and colleagues, 2019, randomised placebo-controlled study of an ashwagandha extract in stressed adults, PMC6750292 (DOI 10.1097/MD.0000000000017186)
• Gopukumar and colleagues, 2021, ashwagandha root extract and cognitive functions in healthy, stressed adults, PMC8632422 (DOI 10.1155/2021/8254344)
• White and colleagues, 2016, randomised crossover trial of an L-theanine based nutrient drink, PMC4728665 (DOI 10.3390/nu8010053)
• Vuong and colleagues, 2011, L-theanine: properties, synthesis and isolation from tea, PubMed 21735448

You can find more of our guides on the Pure Vitamins UK home page.

Warmly,
Dr. Miron, Founder of Pure Vitamins UK

This article is for general information and education. Food supplements are not a substitute for a varied, balanced diet and a healthy lifestyle, and this is not medical advice. If you have symptoms or a health condition, speak to your GP or pharmacist.