L-Lysine and L-Arginine Together

Quick answer

Lysine and arginine are both amino acids, and the one trial that gave them together used 2.64 g of each a day for a week in 108 healthy adults. Its authors worked for a lysine maker, and a 2007 review notes that lysine competes with arginine for transport into cells. Neither has a recommended supplement dose.^1,2,3

Key facts

The one trial we found of the pair gave 2.64 g of lysine and 2.64 g of arginine a day for a week to 108 healthy adults, and its authors worked for a lysine maker.¹
A 2007 review states that lysine competes with arginine for transport into the cell.²
NIH finds that 2 to 20 g of arginine a day has little to no effect on exercise performance, so no benefit is claimed for arginine on this site.³
Adults need about 30 mg of lysine per kg of body weight a day, about 2.1 g for a 70 kg adult, and fewer than 1% of US adults eat less than the average requirement.^4,5
Single doses of arginine above about 9 g often cause stomach and gut discomfort, while pooled studies of lysine found side effects no more common than without it.^6,7

Related amino acids that behave differently

Lysine is one of the nine essential amino acids, with histidine, isoleucine, leucine, methionine, phenylalanine, threonine, tryptophan and valine, that people must get from food.⁸

Adults make arginine mainly in the kidneys, from citrulline produced in the small intestine.^3,9

The difference matters for this pairing. Lysine has to be eaten, because the body cannot make it. Arginine the body does make, and a typical diet adds about 4.4 g a day on top of that, so a supplement of either is adding to a supply that is usually already there.^9,10

What the evidence grades say

Only one claim connects the two, and it is graded early. Arginine has no graded benefit on this site, because NIH found that studies of arginine for exercise showed little to no effect.^1,3

Taken with arginine, may ease feelings of stress*^1,11

Early evidence

Two trials, both run by a company that makes lysine. In 108 healthy Japanese adults, 2.64 g of lysine plus 2.64 g of arginine a day for a week lowered scores on standard questionnaires about tension and worry, and lowered the stress hormone cortisol in men, compared with placebo. In a three-month trial in Syrian communities whose diet relied on wheat, lysine-fortified flour lowered the cortisol response to a blood draw in women and a measure of everyday worry in men. One tested a combination and the other involved people whose diets were low in lysine, so neither shows what lysine alone does for people who eat enough protein.

Amount studied: 2.64 g of lysine with 2.64 g of arginine a day for one week, or lysine-fortified wheat flour for three months

NIH concludes that 2 to 20 g of arginine a day has little to no effect on performance in aerobic or anaerobic exercise, and that there is little scientific backing for its use to add strength, performance or recovery.^3,12

Do they compete?

A 2007 review says lysine competes with arginine for transport into the cell. Its abstract does not say whether that matters at the amounts in supplements, and none of the sources we read measured how well the pair is absorbed in healthy people.²

In adults, about 40% of the arginine eaten is broken down in the small intestine before it reaches the bloodstream.⁹

More often than not, studies tested arginine combined with other ingredients, such as branched-chain amino acids and lysine, rather than on its own.³

The gut shows a clearer difference. A review of arginine's digestive effects found that L-arginine, but not lysine, triggers nitric oxide driven water and electrolyte secretion in the gut, which may be why large single doses can loosen stools. Across 71 human studies of lysine, nausea and stomach ache were not more common than without it.^6,7

Amounts, side by side

What the sources describe, and what our labels give^1,3,4,7,9
	L-arginine	L-lysine
Typical intake from food	About 4.4 g a day in the US	Requirement of about 2.1 g a day for a 70 kg adult
Amounts in studies	2 to 20 g a day for up to 3 months	About 17 mg to 17,500 mg a day, for 1 day to 3 years
In the pair trial	2.64 g a day for a week	2.64 g a day for a week
Ceiling the sources describe	Up to 9 g a day for days or weeks is described as well tolerated	A provisional no-observed-adverse-effect level of 6,000 mg a day
In our products	300 mg in Ashwagandha Complex	100 mg in our elderberry product

Both of our products sit far below the trial amounts. The 300 mg of arginine is about 11% of 2.64 g and the 100 mg of lysine is about 4%, so the pair trial says little about what those labels deliver.¹

Best time to take them

In 10 healthy volunteers, a single 10 g dose of arginine by mouth reached its highest level in the blood about 1 hour after it was taken, at roughly 50 mcg per mL against a usual level near 15 mcg per mL. About 20% of the dose reached the bloodstream.¹³

That is all the timing there is. No source we read gives a time for lysine, and the pair trial's abstract does not describe one, so the best time for the pair has not been tested.^1,13

What's in ours

What’s in ours

Ashwagandha Complex: L-Arginine, 300 mg per serving, from the label

What’s in ours

Immune Support: L-Lysine, 100 mg per serving, from the label

Cautions and who should ask first

In a 2006 trial, 153 people who had just had a first heart attack took 3 g of arginine three times a day or a placebo for 6 months, alongside standard care. Arginine did not change the heart and blood vessel measures studied, 6 people taking it died against none on placebo, and the safety committee stopped enrollment.¹⁴

Arginine can lower blood pressure. NIH notes a slight drop at 9 to 30 g a day, and a 2022 pooled analysis of 22 trials found systolic pressure about 6.4 mmHg and diastolic pressure about 2.6 mmHg lower than with placebo, with the systolic drop seen from about 4 g a day.^3,15

A 2007 review of clinical trials found that single doses of 3 to 6 g rarely caused side effects. Most nausea, vomiting and diarrhea came with single doses above 9 g (more than about 140 mg per kg of body weight), often as part of a daily total near 30 g or more. The effects seemed to depend on how the amount was taken, and they disappeared when it was divided into smaller doses.⁶

A 1996 case report described a 44-year-old woman who developed Fanconi syndrome and tubulointerstitial nephritis, serious kidney damage that progressed to chronic kidney failure, in association with taking lysine. It is a single case.¹⁶

Do not use arginine after a recent heart attack, because more people died on arginine than on placebo in a 2006 trial.¹⁴
Ask first about arginine if you take medicine for blood pressure or for your heart or blood vessels, or if your blood pressure tends to run low.^3,15
Ask first about either one if you have kidney disease or reduced kidney function, are pregnant or nursing, or are under 18.^16,17
The official sources we checked do not document a medicine interaction for lysine or for arginine, but the drug labels we read do not address these supplements either way, so ask a pharmacist if you take any prescription medicine.

Questions people ask

Can you take L-lysine and L-arginine together?

No source we read says not to, and one week-long trial gave 2.64 g of each a day to 108 healthy adults. The caution is arginine's own: it can lower blood pressure, large single doses upset the stomach, and it should not be used after a recent heart attack. Ask a doctor first if you take medicine for your heart or blood pressure.^1,14,15

Does lysine block arginine?

A 2007 review says lysine competes with arginine for transport into the cell. Its abstract does not say how much that matters at supplement amounts, and the studies of the pair did not measure it.²

What is the best time to take L-lysine and L-arginine?

No source gives a time for the pair. A single 10 g dose of arginine reached its highest level in the blood about an hour after it was taken, and no timing data for lysine turned up in the sources we read.¹³

Do lysine and arginine work together for stress?

Only weakly. The sources we read include two trials of lysine for feelings of stress, one of them with arginine, and both were run by a lysine maker. It is graded early, and the one that tested the pair lasted a week.^1,11

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Sources

*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.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.