Last updated: November 2026 · By Tyler, cofounder of Avantera Health · Medically reviewed by Jill Ingenito, DO, FACOG
The short answer: Caffeine and L-theanine are one of the most studied pairings in nootropic research. Of the 15 placebo-controlled trials summarized below, 10 reported a benefit of the pair on attention, alertness or reaction time, usually measured 30 to 90 minutes after a dose. The other 5 found no benefit beyond caffeine alone or placebo. Two meta-analyses pooled this research and found small-to-moderate short-term benefits (Camfield et al., 2014; Payne et al., 2025).
- L-theanine is an amino acid found in tea leaves. Caffeine is the familiar stimulant in coffee and tea.
- Trials paired 40 to 250 mg of caffeine with 50 to 250 mg of L-theanine. Most athlete trials dosed by body weight.
- Researchers tested ratios from about 0.67 to 2.4 parts L-theanine per part caffeine. No trial compared ratios head to head.
- Whether L-theanine takes the edge off caffeine is still debated: one trial found no drop in jitteriness, while a pooled look at two others found slightly lower jitteriness ratings with the pair than with placebo.
- The FDA cites 400 mg of caffeine a day as an amount not generally linked to negative effects for most adults.
Where this article comes from
We first published this post in 2021 and rewrote it in November 2026 around the published trials. Every study number comes from a peer-reviewed paper, a published review or a public agency, listed under Sources at the end. We checked the Avantera Elevate product page on November 5, 2026 for the amounts quoted in the Elevate section. The studies cited here tested individual ingredients, at the amounts and in the groups described. They aren't studies of Avantera products.
What are caffeine and L-theanine, and why are they paired?
Caffeine works mainly by blocking adenosine, a brain chemical that builds up while you're awake and makes you feel tired (McLellan et al., 2016). Its best-supported effects are on alertness, vigilance, attention and reaction time. We cover caffeine on its own in Is Caffeine a Nootropic?
L-theanine is an amino acid found in tea leaves. After a 100 mg dose, it reached its highest level in the blood in under an hour (Scheid et al., 2012). How it works in people is less settled than for caffeine. The common explanation, that it dampens excitatory signaling in the brain, comes mostly from animal research.
Both occur together in tea, which is how researchers first came to test them as a pair. The question the trials ask is simple: does adding L-theanine change what caffeine does for focus and alertness?
What did the caffeine and L-theanine trials find?
These are the placebo-controlled trials of the combination on focus and performance in our research file, ordered from the most L-theanine per part caffeine to the least. All tested a single dose.
| Trial | Caffeine | L-theanine | L-theanine per part caffeine | Who took part | What the pair did vs placebo |
|---|---|---|---|---|---|
| Giesbrecht et al., 2010 | 40 mg | 97 mg | About 2.4 to 1 | 44 young adults | Better task-switching accuracy and self-rated alertness, less tiredness; no effect on visual search, choice reaction time or mental rotation |
| Einöther et al., 2010 | 40 mg | 97 mg | About 2.4 to 1 | Healthy adults (number not in the abstract) | Better task switching; no change in self-rated alertness |
| Owen et al., 2008 | 50 mg | 100 mg | 2 to 1 | 27 healthy adults | Faster, more accurate task switching at 60 minutes; less distracted on a memory task at 60 and 90 minutes |
| Kelly et al., 2008 | 50 mg | 100 mg | 2 to 1 | Healthy adults (number not in the abstract) | Higher hit rate and better target discrimination; L-theanine alone had no effect |
| Foxe et al., 2012 | 50 mg | 100 mg | 2 to 1 | 27 healthy adults | Caffeine and L-theanine each cut errors over a two-hour task; the pair added nothing over either one alone |
| Haskell et al., 2008 | 150 mg | 250 mg | About 1.7 to 1 | Healthy adults (number not in the abstract) | Faster simple and working-memory reaction times, better accuracy on two tasks, more self-rated alertness, less mental fatigue |
| Kahathuduwa et al., 2017 | 160 mg | 200 mg | 1.25 to 1 | 20 healthy men | Faster recognition reaction time; a larger attention-related brain signal than either ingredient alone |
| Kahathuduwa et al., 2018 | 160 mg | 200 mg | 1.25 to 1 | 9 healthy men (brain imaging) | Faster responses to targets; less activity in mind-wandering brain regions |
| Nawarathna et al., 2025 | 160 mg | 200 mg | 1.25 to 1 | 37 young adults after a night without sleep | Better hit rate, discrimination and reaction time on an attention task |
| Giles et al., 2017 | 200 mg | 200 mg | 1 to 1 | 36 adults viewing upsetting images | No different from placebo |
| Yilmaz et al., 2023 | 6 mg per kg | 6 mg per kg | 1 to 1 | 22 elite curling athletes | Best Stroop speed and accuracy and best shot scores of the arms tested |
| Razazan et al., 2025 | 3 mg per kg | 3 mg per kg | 1 to 1 | 12 elite wrestlers | Best strength and Stroop results of the arms tested |
| Tuncer et al., 2025 | 3 mg per kg | 200 mg | Varies with body weight | 20 trained athletes | No added benefit from the pair |
| Rogers et al., 2008 | 250 mg | 200 mg | 0.8 to 1 | 48 healthy adults | Adding L-theanine did not change caffeine's effect on jitteriness or alertness |
| Dodd et al., 2015 | 75 mg | 50 mg | About 0.67 to 1 | 24 healthy adults | Adding L-theanine erased caffeine's attention and mood benefits |
Two reviews put these results together. A 2014 meta-analysis of 11 placebo-controlled studies found that caffeine and L-theanine taken together supported alertness and attention switching in the first two hours (Camfield et al., 2014). A 2025 review of 50 randomized trials in healthy people found small-to-moderate short-term benefits for attention when L-theanine was paired with caffeine, while noting the evidence is still uncertain (Payne et al., 2025). Across the pairing arms in that review, the median amounts were about 82 mg of L-theanine and 89 mg of caffeine.
Is there a best ratio of L-theanine to caffeine?
No trial has tested one ratio against another, so no ratio has been shown to be best. The well-known "2 to 1" figure comes from a cluster of early trials that paired 40 to 50 mg of caffeine with 97 to 100 mg of L-theanine. Positive results also came from trials at 1.25 to 1, which used 160 mg of caffeine with 200 mg of L-theanine, and from 1 to 1 trials in athletes.
Two patterns are worth knowing. The two trials with more caffeine than L-theanine (Rogers 2008 and Dodd 2015) were the least favorable for the pair, though that is an observation across two studies, not a tested effect. And in the 2014 meta-analysis, the amount of caffeine explained more of the effect than the amount of L-theanine (Camfield et al., 2014).
Does L-theanine stop caffeine jitters?
The evidence that L-theanine takes the edge off caffeine is suggestive and mixed. In a 2008 trial with 250 mg of caffeine, adding 200 mg of L-theanine did not lower self-rated jitteriness (Rogers et al., 2008). In a 2015 trial, no combination changed jitteriness ratings (Dodd et al., 2015). The 2025 review pooled two trials and found slightly lower jitteriness and headache ratings with the pair than with placebo (Payne et al., 2025).
A fair way to describe the pair is calm, focused alertness in many trials, rather than a guaranteed fix for caffeine's side effects. If caffeine tends to make you jittery, the amount of caffeine is still the first thing to look at.
How fast do caffeine and L-theanine work, and how long do they last?
Trials measured effects of the pair as early as 10 minutes after a dose (Einöther et al., 2010) and 20 minutes (Giesbrecht et al., 2010), and most often at 50 to 90 minutes (Owen et al., 2008; Kahathuduwa et al., 2017; Nawarathna et al., 2025). The clearest pooled effects fell in the first two hours (Camfield et al., 2014).
Caffeine stays in the body longer than the measured lift. Its half-life in adults is about 3 to 7 hours (Temple et al., 2017). A 2023 analysis estimated that a coffee-sized dose should be taken at least 8.8 hours before bed to avoid losing sleep time (Gardiner et al., 2023). That is why a caffeinated supplement is best taken in the morning.
How much caffeine and L-theanine is safe?
- Caffeine, per day. The FDA cites 400 mg a day, about two to three 12-ounce cups of coffee, as an amount not generally linked to negative effects for most adults.
- Caffeine, at once. Europe's food-safety agency considers single doses up to 200 mg safe for healthy adults (EFSA, 2015).
- L-theanine. A 2026 meta-analysis of 31 randomized trials reported no serious adverse events with L-theanine (Gerolymos et al., 2026).
- Who should check first. If you're pregnant, trying to become pregnant or breastfeeding, the FDA recommends talking with your health care provider about caffeine. If you take any medication, have a medical condition or are under 18, check with a clinician before using a caffeine product.
What people claim about caffeine and L-theanine, checked against the trials
| What you'll read | What the trials show |
|---|---|
| "2 to 1 is the proven ratio" | Not tested. Positive trials ran from 1 to 1 up to about 2.4 to 1, and no trial compared ratios directly. |
| "L-theanine cancels caffeine's jitters" | Mixed. One trial found no change in jitteriness; two pooled trials found slightly lower ratings with the pair than with placebo. |
| "The pair always beats caffeine alone" | Not always. Foxe 2012, Giles 2017 and Tuncer 2025 found no added benefit, and in Dodd 2015 adding L-theanine erased caffeine's benefits. |
| "It works within minutes" | Effects were measured from 10 minutes to 2 hours after a dose, most often at 50 to 90 minutes. |
| "L-theanine alone does the same job" | Sometimes, on some tasks. A single 200 mg dose sped choice reaction time in a 2026 meta-analysis, while 50 to 100 mg alone had no effect in two of the pairing trials (Kelly 2008; Dodd 2015). |
How this applies to Elevate
Avantera Elevate contains both ingredients. A cup of coffee's caffeine, with twice the L-theanine for calm, steady focus.* Each serving pairs 95 mg of caffeine (from green tea leaf) with 200 mg of L-theanine. Elevate Sour Gummies have the same 95 mg of caffeine, from green coffee bean extract, with 200 mg of L-theanine. The two are compared line by line in Elevate capsules vs Elevate Sour Gummies.
Caffeine and L-theanine are two of the nine ingredients in Elevate. Elevate supports acetylcholine, your brain's memory messenger, two ways: CDP-choline and bacopa.* For how each ingredient has been studied, see our guide to the best nootropic ingredients for focus. If daytime energy is what you're after, we put the caffeine on popular labels side by side in our guide to energy supplements, and we compare a nootropic with your usual cup in Nootropics vs Coffee.
Nine ingredients. Every dose on the label. About $1.78 a day. Avantera Elevate lists all nine ingredients and every dose on the label, with no proprietary blends, and every batch is third-party tested. Elevate's certificate of analysis is posted on our quality page.
Because Elevate has caffeine, the timing and daily-limit points above apply to it. Our product page directs taking it within the first hour of waking, and suggests that people sensitive to caffeine check their tolerance with one capsule before taking the full two-capsule serving.
Elevate costs $49.95 for a 28-day supply, about $1.78 a day, with a 30-day money-back guarantee on your first order. Elevate ships as a subscription every 4 weeks, and you can pause, skip or cancel anytime from your account. The full label is on the Avantera Elevate product page, and what customers say about it is on our Avantera Elevate reviews page.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Medically reviewed by Jill Ingenito, DO, FACOG. Dr. Ingenito is a board-certified obstetrician-gynecologist with about 18 years in clinical practice. Read how our medical reviewers work with Avantera.
Frequently asked questions
What does L-theanine do with caffeine?
In most placebo-controlled trials of the pair, caffeine with L-theanine supported attention, alertness or reaction time within about 30 to 90 minutes. Two meta-analyses found small-to-moderate short-term benefits. Some trials found the pair no better than caffeine alone.
What is the best ratio of L-theanine to caffeine?
No trial has compared ratios directly. Trials with positive results used from 1 to 1 up to about 2.4 parts L-theanine per part caffeine. The two trials with more caffeine than L-theanine were the least favorable for the pair.
How much caffeine and L-theanine did the studies use?
Fixed-dose trials paired 40 to 250 mg of caffeine with 50 to 250 mg of L-theanine. Athlete trials dosed caffeine by body weight, at 3 to 6 mg per kilogram, and two of them dosed L-theanine the same way.
Does L-theanine stop caffeine jitters?
The evidence is mixed. One trial found adding L-theanine did not lower self-rated jitteriness, while a 2025 review that pooled two trials found slightly lower jitteriness ratings with the pair than with placebo.
How long does caffeine with L-theanine take to work?
Trials measured effects from 10 minutes to 2 hours after a dose, most often at 50 to 90 minutes. Caffeine's half-life in adults is about 3 to 7 hours, so a morning dose is best.
How much caffeine and L-theanine is in Avantera Elevate?
Each serving of Avantera Elevate (2 capsules) has 95 mg of caffeine (from green tea leaf) with 200 mg of L-theanine. A serving of Elevate Sour Gummies (3 gummies) also has 95 mg of caffeine, from green coffee bean extract, with 200 mg of L-theanine.
Sources
- Camfield DA, Stough C, Farrimond J, Scholey AB. Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis. Nutrition Reviews, 2014. PubMed
- Payne ER, Aceves-Martins M, Dubost J, et al. Effects of tea (Camellia sinensis) or its bioactive compounds L-theanine or L-theanine plus caffeine on cognition, sleep, and mood in healthy participants: a systematic review and meta-analysis of randomized controlled trials. Nutrition Reviews, 2025. PubMed
- Gerolymos C, Saddier E, Boyer L, Fond G. Cognitive and affective effects of L-theanine: a systematic review and meta-analysis of 31 randomized trials. Molecular Psychiatry, 2026. PubMed
- Giesbrecht T, Rycroft JA, Rowson MJ, De Bruin EA. The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. Nutritional Neuroscience, 2010. PubMed
- Einöther SJ, Martens VE, Rycroft JA, De Bruin EA. L-theanine and caffeine improve task switching but not intersensory attention or subjective alertness. Appetite, 2010. PubMed
- Owen GN, Parnell H, De Bruin EA, Rycroft JA. The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutritional Neuroscience, 2008. PubMed
- Kelly SP, Gomez-Ramirez M, Montesi JL, Foxe JJ. L-theanine and caffeine in combination affect human cognition as evidenced by oscillatory alpha-band activity and attention task performance. Journal of Nutrition, 2008. PubMed
- Foxe JJ, Morie KP, Laud PJ, et al. Assessing the effects of caffeine and theanine on the maintenance of vigilance during a sustained attention task. Neuropharmacology, 2012. PubMed
- Haskell CF, Kennedy DO, Milne AL, Wesnes KA, Scholey AB. The effects of L-theanine, caffeine and their combination on cognition and mood. Biological Psychology, 2008. PubMed
- Kahathuduwa CN, Dassanayake TL, Amarakoon AMT, Weerasinghe VS. Acute effects of theanine, caffeine and theanine-caffeine combination on attention. Nutritional Neuroscience, 2017. PubMed
- Kahathuduwa CN, Dhanasekara CS, Chin SH, et al. L-theanine and caffeine improve target-specific attention to visual stimuli by decreasing mind wandering: a human functional magnetic resonance imaging study. Nutrition Research, 2018. PubMed
- Nawarathna GS, Ariyasinghe DI, Dassanayake TL. High-dose L-theanine-caffeine combination improves neurobehavioural and neurophysiological measures of selective attention in acutely sleep-deprived young adults. British Journal of Nutrition, 2025. PubMed
- Giles GE, Mahoney CR, Brunyé TT, et al. Caffeine and theanine exert opposite effects on attention under emotional arousal. Canadian Journal of Physiology and Pharmacology, 2017. PubMed
- Yilmaz U, Buzdagli Y, Polat ML, et al. Effect of single or combined caffeine and L-theanine supplementation on shooting and cognitive performance in elite curling athletes: a double-blind, placebo-controlled study. Journal of the International Society of Sports Nutrition, 2023. PubMed
- Razazan R, Hemmatinafar M, Imanian B, et al. Performance-enhancing effects of caffeine and L-theanine among Iranian elite wrestlers: a focus on cognitive and specific physical performance. Journal of the International Society of Sports Nutrition, 2025. PubMed
- Tuncer SY, Ozdenk S, Yildirim UC, et al. Acute effects of combined and isolated caffeine and theanine supplementation on physical and cognitive performance in competitive athletes: a randomized, double-blind, placebo-controlled crossover study. Frontiers in Nutrition, 2025. PubMed
- Rogers PJ, Smith JE, Heatherley SV, Pleydell-Pearce CW. Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together. Psychopharmacology, 2008. PubMed
- Dodd FL, Kennedy DO, Riby LM, Haskell-Ramsay CF. A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood. Psychopharmacology, 2015. PubMed
- Scheid L, Ellinger S, Alteheld B, et al. Kinetics of L-theanine uptake and metabolism in healthy participants are comparable after ingestion of L-theanine via capsules and green tea. Journal of Nutrition, 2012. PubMed
- McLellan TM, Caldwell JA, Lieberman HR. A review of caffeine's effects on cognitive, physical and occupational performance. Neuroscience and Biobehavioral Reviews, 2016. PubMed
- Temple JL, Bernard C, Lipshultz SE, et al. The safety of ingested caffeine: a comprehensive review. Frontiers in Psychiatry, 2017. PubMed
- Gardiner C, Weakley J, Burke LM, et al. The effect of caffeine on subsequent sleep: a systematic review and meta-analysis. Sleep Medicine Reviews, 2023. PubMed
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific opinion on the safety of caffeine. EFSA Journal, 2015. EFSA
- U.S. Food and Drug Administration. Spilling the beans: how much caffeine is too much? FDA