Quick answer
Women need the same lysine per kg of body weight as men, about 30 mg a day, or roughly 1.8 g at 60 kg, and food usually covers it. Needs rise in late pregnancy, to about 50 mg per kg in one study. The supplement trials that included women are small, and their results are graded early.1,2,3
Key facts
- In five healthy women, the lysine requirement was 35.0 mg per kg a day in the first half of the menstrual cycle and 37.7 mg in the second half.4
- Early in pregnancy, the measured requirement was about 37 mg per kg a day, close to that of other adults.2
- Fewer than 1% of US adults, women included, eat less lysine than the average requirement.5
- Plant protein isolates averaged about half the lysine of animal proteins.6
How much lysine women need
WHO gives a single adult figure, about 30 mg per kg of body weight a day, so a woman's need scales with her weight rather than her sex: about 1.5 g at 50 kg, 1.8 g at 60 kg and 2.1 g at 70 kg.1
In a study of five healthy women, the lysine requirement was 35.0 mg per kg a day in the first half of the menstrual cycle and 37.7 mg per kg in the second half.4
The difference across the cycle is small, under 8%, and the researchers put it down to faster breakdown of amino acids in the second half. It comes from a study of five women and describes needs met by food, not a reason to supplement at certain times of the month.4
Pregnancy and breastfeeding
In a study of 33 healthy pregnant women, the requirement measured about 37 mg per kg a day at 12 to 19 weeks and about 50 mg per kg at 33 to 39 weeks. The later figure is about 23% above the current US estimate for pregnancy of 41 mg per kg.2
Those needs were met by controlled meals, not supplements. We found no safety data on lysine supplements in pregnancy or breastfeeding, so protein foods are the way to cover the extra, and any supplement is a question for your doctor.2,7
Plant-based diets
Combining different plant proteins, or plant and animal proteins, gives a blend whose amino acid profile is closer to that of animal protein.6
Women who eat little or no animal food can still meet the requirement with legumes such as soy, which carry more lysine than the requirement pattern. Diets built mostly on wheat, rice or maize are the ones that tend to fall short.1
What the evidence shows for women
Two of the graded claims are especially relevant here: the nutrient role, which applies to everyone, and the calcium study, which began with 30 women.
Provides lysine, an essential amino acid the body uses to build protein*1,5,8,9
Moderate evidence
A well-established nutrient function. Lysine is one of nine essential amino acids that must come from the diet for the body to keep building protein, as NIH and a 2020 review of lysine metabolism describe. An expert panel for WHO, FAO and UNU puts the adult requirement at about 30 mg per kg of body weight a day. In US survey data, fewer than 1% of adults fall below the average requirement, so for most people food already covers it and extra lysine adds little.
Amount studied: Requirement: about 30 mg per kg of body weight a day from all food, or about 2.1 g for a 70 kg adult
May help the body absorb and hold on to calcium*3
Early evidence
One small study from 1992. When 30 women took a large calcium dose, adding 400 mg of lysine blunted the rise in calcium lost in urine in the 15 healthy women. In a second part, 45 people under medical care absorbed more calcium while taking 800 mg of lysine a day than while taking two other amino acids. We found no larger or longer trial.
Amount studied: 400 mg with a single calcium dose, or 800 mg a day for a short period
The stress trials included women too. In the Syrian study, the hormone response to a blood draw fell in women on lysine-fortified flour; in the Japanese study, questionnaire scores fell in both sexes but the hormone change was seen only in men.10,11
What's in ours
What’s in ours
- Immune Support: L-Lysine, 100 mg per serving, from the label
For a 60 kg woman, the 100 mg in the product above is about 6% of her daily requirement.1
Who should ask first
- Ask your doctor before taking lysine if you are pregnant or breastfeeding
- Ask first if you have kidney disease or reduced kidney function; a 1996 case report described serious kidney damage in a woman taking lysine12
- Ask your pharmacist if you take prescription medicines, including thyroid medicine; the official labels we checked do not address lysine either way13
Questions people ask
What does l-lysine do for women?
The same as for men: it is an essential amino acid used to build protein. One small 1992 study in women suggested it may help the body hold on to calcium, which is graded as early evidence above.3,8
Do women over 50 need more lysine?
WHO found too little data to set a separate figure for older adults, so the general adult figure of about 30 mg per kg a day applies to them too.1
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Sources
- Joint WHO/FAO/UNU Expert Consultation. Protein and amino acid requirements in human nutrition. World Health Organ Tech Rep Ser. 2007;(935):1-265. Opened 2026-10-07.
- Payne M, Stephens T, Lim K, Ball RO, Pencharz PB, Elango R. Lysine Requirements of Healthy Pregnant Women are Higher During Late Stages of Gestation Compared to Early Gestation. J Nutr. 2018;148(1):94-99. Opened 2026-10-07.
- Civitelli R, Villareal DT, Agnusdei D, Nardi P, Avioli LV, Gennari C. Dietary L-lysine and calcium metabolism in humans. Nutrition. 1992;8(6):400-405. Opened 2026-10-07.
- Kriengsinyos W, Wykes LJ, Goonewardene LA, Ball RO, Pencharz PB. Phase of menstrual cycle affects lysine requirement in healthy women. Am J Physiol Endocrinol Metab. 2004;287(3):E489-E496. Opened 2026-10-07.
- Berryman CE, Cheung SN, Collette EM, Pasiakos SM, Lieberman HR, Fulgoni VL 3rd. Amino Acid Intake and Conformance With the Dietary Reference Intakes in the United States: Analysis of the National Health and Nutrition Examination Survey, 2001-2018. J Nutr. 2023;153(3):749-759. Opened 2026-10-07.
- Gorissen SHM, Crombag JJR, Senden JMG, et al. Protein content and amino acid composition of commercially available plant-based protein isolates. Amino Acids. 2018;50(12):1685-1695. Opened 2026-10-07.
- Hayamizu K, Oshima I, Fukuda Z, et al. Safety assessment of L-lysine oral intake: a systematic review. Amino Acids. 2019;51(4):647-659. Opened 2026-10-07.
- National Institutes of Health, Office of Dietary Supplements. Dietary Supplements for Exercise and Athletic Performance: Fact Sheet for Health Professionals. Updated April 1, 2024. Opened 2026-10-07.
- Matthews DE. Review of Lysine Metabolism with a Focus on Humans. J Nutr. 2020;150(Suppl 1):2548S-2555S. Opened 2026-10-07.
- Smriga M, Ghosh S, Mouneimne Y, Pellett PL, Scrimshaw NS. Lysine fortification reduces anxiety and lessens stress in family members in economically weak communities in Northwest Syria. Proc Natl Acad Sci U S A. 2004;101(22):8285-8288. Opened 2026-10-07.
- Smriga M, Ando T, Akutsu M, Furukawa Y, Miwa K, Morinaga Y. Oral treatment with L-lysine and L-arginine reduces anxiety and basal cortisol levels in healthy humans. Biomed Res. 2007;28(2):85-90. Opened 2026-10-07.
- Lo JC, Chertow GM, Rennke H, Seifter JL. Fanconi's syndrome and tubulointerstitial nephritis in association with L-lysine ingestion. Am J Kidney Dis. 1996;28(4):614-617. Opened 2026-10-07.
- Synthroid (levothyroxine sodium) tablets: prescribing information (AbbVie). DailyMed, U.S. National Library of Medicine. Published February 29, 2024. Opened 2026-10-07.
*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.