L-Theanine and Magnesium: Can You Take Them Together?
In this article
L-theanine and magnesium are two of the most popular supplements for feeling calmer and sleeping better, and they are often sold together. Can you take them at the same time, and does the combination do anything special? Here is what each one does, what the evidence shows, the doses to stay within and a simple way to fit both into your day, including with d9-caffeine in the morning.
What L-theanine does
L-theanine is an amino acid found naturally in tea. During the day, it is best studied as a partner to caffeine: in human trials, the pairing improved attention-switching and alertness, and L-theanine blunted the rise in blood pressure that caffeine produced. At night, a 2019 study of 30 adults taking 200 mg at bedtime for four weeks found that some sleep measures, such as how long it took to fall asleep, improved compared with placebo, though the authors described the effects as modest. In 2007, the FDA had no questions about its GRAS status at up to 250 mg per serving.
What magnesium does
Magnesium is an essential mineral involved in hundreds of processes, including muscle and nerve function. Many adults fall short of the recommended intake. For sleep, the evidence is limited: a 2021 review of three small trials in older adults found people fell asleep about 17 minutes faster on magnesium, but rated the quality of the evidence as low to very low.
Can you take them together?
For most healthy adults, yes. There is no known interaction between L-theanine and magnesium. What is missing is evidence that the pair works better together: we did not find any human study testing L-theanine and magnesium on their own as a combination. Most products that contain both also add other ingredients, so their results cannot be credited to the pair.
Safe amounts
| L-theanine | Magnesium | |
|---|---|---|
| Typical amounts | About 50 to 250 mg per serving in studies | Recommended daily intake 310 to 420 mg from all sources, depending on age and sex |
| Upper limit | GRAS notice covers up to 250 mg per serving | 350 mg a day from supplements, above which diarrhea becomes more likely |
| Watch for | Drowsiness; caution with blood pressure medication and sedatives | Interactions with some antibiotics, bisphosphonates, diuretics and acid-reducing drugs |
The 350 mg upper limit for magnesium applies to supplements and medications, not to magnesium in food.
A simple daytime and evening routine
The two fit naturally at different times of day:
- Morning: L-theanine paired with caffeine for calm, focused energy. Caffeine 2.0 + L-Theanine combines 50 mg of L-theanine with 22.5 mg of d9-caffeine in each capsule.
- Evening: magnesium, if you choose to take it, with dinner or before bed, staying within 350 mg a day from supplements.
d9-caffeine is caffeine with nine hydrogen atoms replaced by deuterium, which slows how fast the liver breaks it down. In a 2022 double-blind study, it was absorbed as quickly as regular caffeine and produced four to five times the total exposure over time, which is exactly why it belongs in the morning and not near bedtime. Our guide to L-theanine dosage has more on timing.
Who should check with a physician first
Talk to your physician before taking magnesium supplements if you have kidney disease, and check with your pharmacist about timing if you take antibiotics, bisphosphonates, diuretics or acid-reducing medication. Skip Caffeine 2.0 + L-Theanine, or talk to your physician first, if you are pregnant or breastfeeding, under 18, sensitive to caffeine, or have a heart condition, high blood pressure, an arrhythmia, an anxiety disorder or a sleep disorder, and check with your physician or pharmacist if you take prescription medication, including blood pressure medication or sedatives.
How Vita Bloom fits
Caffeine 2.0 + L-Theanine pairs 22.5 mg of patented Deura9® d9-caffeine with 50 mg of L-theanine in every capsule. Take it in the morning, starting with one capsule, up to four a day, and never more than 90 mg of d9-caffeine.
Frequently asked questions
Can I take L-theanine and magnesium at the same time?
For most healthy adults, yes. There is no known interaction, though there is little research on the pair as a combination.
Is L-theanine or magnesium better for sleep?
Both have modest evidence. L-theanine improved some sleep measures in a small 2019 trial; magnesium shortened time to fall asleep in small trials of older adults with low-quality evidence.
How much magnesium is too much?
The upper limit from supplements is 350 mg a day for adults. Higher amounts commonly cause diarrhea.
Can I take Caffeine 2.0 + L-Theanine at night?
No. It contains d9-caffeine, which lasts longer than regular caffeine. Take it in the morning.
Deura9® is a registered trademark of Lennham Pharmaceuticals, Inc. under exclusive license to d9 Designs Inc.
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.
Educational information, not personal medical advice. Ingredient research does not establish that a finished supplement treats or prevents a disease. Follow your product label and ask your healthcare professional about personal suitability.
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