Quick answer

Adults need about 30 mg of lysine per kg of body weight a day from food, roughly 2.1 g at 70 kg, and most people already eat more than that. Supplement studies have used anywhere from about 17 mg to 17,500 mg a day, and a 2019 review set 6,000 mg a day as a provisional no-adverse-effect level.^1,2,3

Key facts

WHO's safe intake for lysine is about 24% above the average requirement, near 37 mg per kg a day.¹
Late in pregnancy, one study measured an average need of about 50 mg per kg a day.⁴
A 1,000 mg tablet is about half the daily requirement of a 70 kg adult.¹
Fewer than 1% of US adults eat less lysine than the average requirement.²

The daily requirement by body weight

Lysine a day from all food, by body weight¹
Body weight	Average requirement (30 mg per kg)	Safe intake (about 37 mg per kg)
50 kg (110 lb)	1.5 g	1.9 g
60 kg (132 lb)	1.8 g	2.2 g
70 kg (154 lb)	2.1 g	2.6 g
80 kg (176 lb)	2.4 g	3.0 g
90 kg (198 lb)	2.7 g	3.3 g

The average requirement is a midpoint; the safe intake, 24% higher, allows for people whose needs are above average. WHO gives one adult figure for women and men and, lacking separate data, applies it to older adults as well.¹

The figure was not easy to pin down. WHO's estimate rests on tracer studies of amino acid use, and the report notes that a value somewhere between 22 mg and 30 mg per kg cannot be ruled out.¹

What food already provides

In US national survey data from 2001 to 2018, fewer than 1% of adults ate less than the average requirement for any essential amino acid, lysine included.²

Put another way, the requirement is a floor that ordinary diets clear. A supplement adds to what food supplies rather than replacing it. The people most likely to fall short are those whose protein comes mostly from cereals, where lysine is the amino acid in shortest supply.^1,2

Pregnancy

A study of 33 pregnant women measured an average requirement of about 37 mg per kg a day early in pregnancy and about 50 mg per kg late in pregnancy, above the current US estimate of 41 mg per kg.⁴

That study measured needs on a controlled diet; it did not test supplements. Ask your doctor before taking a lysine supplement while pregnant or breastfeeding.⁴

Amounts used in studies

Human studies of lysine supplements have used from about 17 mg to 17,500 mg a day, for anywhere from 1 day to 3 years.³

The trials behind the graded claims used very different amounts, from 400 mg taken with a single calcium dose to about 80 mg per kg a day in a controlled diet. The two below used the most.^5,6

Taken with arginine, may ease feelings of stress*^7,8

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

May slightly increase muscle strength at very high intakes*⁶

Early evidence

One small trial. Forty young men in India, some of them undernourished, ate controlled diets for 8 weeks that supplied either their usual lysine intake (about 25 to 40 mg per kg of body weight a day) or 80 mg per kg. The high-lysine diet raised muscle strength by about 7.5% but did not change muscle mass or the other measures. Some of the men usually ate less lysine than the requirement, and the study was read as an abstract only.

Amount studied: 80 mg per kg of body weight a day from a controlled diet for 8 weeks, about 5.6 g for a 70 kg man

How much is too much

No official upper limit has been set. A 2019 systematic review of 71 human studies proposed 6,000 mg a day as a provisional level at which no adverse effects were seen, based on gut complaints such as nausea and stomach ache.³

Provisional means just that: only 12 of the 71 studies scored as relatively high quality. People with kidney disease or reduced kidney function should ask a doctor before taking any amount, because of a reported case of kidney damage.^3,9

What's in ours

What’s in ours

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

The 100 mg in the product above is about 5% of the requirement at 70 kg and under 2% of the 6,000 mg provisional level.^1,3

Questions people ask

Is 1,000 mg of l-lysine a day too much?

Not by the available evidence. It is about half the daily requirement of a 70 kg adult, and a 2019 review proposed 6,000 mg a day as a provisional level without adverse effects. Ask a doctor first if you have kidney disease.^1,3

How much lysine is in food?

Protein foods carry it in proportion to their protein. In a lab analysis, lysine made up about 7% of animal proteins such as milk and egg, and about 3.6% of plant protein isolates, so 20 g of animal protein holds roughly 1.4 g of lysine.¹⁰

Do adults need different amounts by sex?

WHO gives one adult figure per kg of body weight, so needs scale with weight. One small study found women's needs shift slightly across the menstrual cycle, from 35.0 to 37.7 mg per kg a day.^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.