Is Lysine Safe During Pregnancy?

Updated September 14, 2026

The Answer

Lysine is likely safe during pregnancy in normal dietary amounts and food additive use. High dose L lysine supplements are a different exposure: pregnancy data are limited, and clinician guidance may be warranted.

The key distinction is lysine from food versus concentrated single amino acid supplements; the reassurance for food does not establish high dose supplement safety.

Human pregnancy requirement research and a 2024 AHRQ systematic review suggest lysine needs may rise in late pregnancy, but the direct evidence base is small and does not establish high dose supplement safety.

Already used it? If you have taken a lysine supplement, check the daily amount on the label and share it with your pregnancy clinician, especially for high dose use.

Pregnancy Safe is 100% independent and research driven. No companies pay to promote or sponsor products.

What Is Lysine?

You may also see it listed as: L-lysine

Lysine is an essential amino acid involved in protein synthesis and collagen production. It occurs in protein foods, is added to some foods, and is sold as L lysine supplements, often marketed for cold sores. You may also encounter it in protein powders, cold sore treatments, and skincare products.

What Other Ingredients Should You Look Out for in Products With Lysine?

A product's full ingredient list determines whether it's pregnancy-safe or not. These ingredients also appear in some of the lysine products we analyzed and may deserve a closer look.

Retinoid

Avoid

Look for retinyl palmitate, a vitamin A derivative, on cold sore treatment labels. Pregnancy guidance discourages topical retinoids despite generally low absorption, so ask a pharmacist or pregnancy clinician to review the formula and intended use.

Flagged in 1 product (25%) in this analysis.

Calendula

Caution

Look for calendula officinalis extract in cold sore treatments and check where the product is intended to be applied. Normal use on intact skin is lower concern, but medicinal wound or mouth preparations lack pregnancy specific safety data, and Asteraceae allergy matters.

Flagged in 2 products (50%) in this analysis.

Propolis

Caution

Propolis extract is a bee derived ingredient found in these cold sore treatments. Check with a pharmacist if you have sensitivities to bee products, poplar products, or balsam of Peru, because propolis can cause allergic reactions.

Flagged in 2 products (50%) in this analysis.

Does the Form or Amount of Lysine Matter During Pregnancy?

Normal dietary lysine and food additive use are low concern. For oral lysine natural health products providing more than 300 mg daily, Health Canada requires pregnancy caution language; this is a labeling threshold, not a proven safety cutoff. Dietary requirement research does not establish the safety of concentrated supplements or topical cold sore preparations.

What Products Contain Lysine?

Pregnancy Safe has looked at 408 products that have lysine as an ingredient. The category and grade breakdowns below use 4 products whose names mention Lysine or another name for it.

What Types of Products Contain Lysine?

Cold Sore Treatment 2 products

Dietary Supplement 2 products

Products You May Have That Contain Lysine

Grade	Product	Brand	Type
F	Lip Clear Lysine + Cold Sore Treatment - 0.25Oz	Lip Clear	Cold Sore Treatment
B+	Lysine 500 Mg	Dr. Clark Research Association Dr. Clark Zentrum	Dietary Supplement
B+	Time C Timed Release With Magnesium And Lysine 1000	Lifelink	Dietary Supplement
F	Quantum Super Lysine Plus Cold Sore Treatment	Quantum Health	Cold Sore Treatment
C+	Swipe Serum Concealer	Tower 28 Beauty	Concealer
C+	Sensitive Skin Body Lotion - 20 Fl Oz - Fragrance Free - Up&Up™	Up&Up	Body Lotion
C	Eucerin Complete Repair Moisturizing Lotion	Eucerin	Moisturizing Lotion
C	Round Lab Skincare 1025 Dokdo Cleansing Oil 200Ml	Round Lab	Cleansing Oil

How Do Products Containing Lysine Score?

It can be helpful to see how products containing lysine generally score during pregnancy. This does not tell you whether your exact product is safe, but it gives you a general idea of what we found. In this breakdown of 4 products, 50% receive a B grade. A B grade means the complete formula is likely safe, with minimal identified risk.

0 (0%)

2 (50%)

0 (0%)

2 (50%)

Frequently Asked Questions About Lysine During Pregnancy

Can I take L lysine supplements for cold sores while pregnant?

L lysine supplements are often marketed for cold sores, but that does not establish their effectiveness or pregnancy safety. High dose supplemental use has limited pregnancy data and warrants discussion with your pregnancy clinician.

Is 300 mg a safe daily supplement limit?

It is not an established pregnancy safety limit. Health Canada requires pregnancy caution language for oral lysine natural health products providing more than 300 mg daily; that does not prove all doses at or below that amount are safe.

Do lysine needs increase during pregnancy?

Human requirement research and a 2024 AHRQ systematic review suggest needs may be higher in late pregnancy, particularly with cereal heavy or low protein diets. The direct evidence is small and does not establish that you need a separate lysine supplement.

What if I took lysine before I knew I was pregnant?

Check whether the exposure was normal food intake or a supplement. Food amounts are low concern; for supplements, share the product label and daily amount with your pregnancy clinician. Limited supplement data cannot determine an individual pregnancy outcome.

Can lysine cause miscarriage?

The available evidence does not establish that lysine causes miscarriage. However, limited pregnancy data for high dose supplements also do not establish their safety; normal dietary lysine remains a separate, low concern exposure.

Does the food guidance apply to lysine cold sore creams?

No. Evidence about dietary lysine does not establish the pregnancy safety of a topical cold sore preparation. The route and other ingredients need separate consideration; lysine alone cannot determine whether the complete formula is suitable.

How Do We Score Products for Pregnancy Safety?

We analyze each product's ingredients and category to flag known risks and provide cautionary notices for general category safety concerns.

A - Safe

Excellent choice! All ingredients are considered safe during pregnancy.

What to do: Use with confidence.

B - Likely Safe

Pretty much safe with very minimal risk. Some ingredients may have limited pregnancy studies, but no significant safety concerns have been identified.

What to do: Use with confidence.

C - Limit

Contains ingredients with some pregnancy considerations. Research shows these ingredients may have limited safety data, potential for minor hormonal effects, or require caution based on animal studies.

What to do: Use sparingly and consider safer alternatives when available.

D - Caution

Similar to C grade but contains multiple cautionary ingredients. The combination increases overall concern.

What to do: Try to avoid if that makes you feel better. If you've already used it, no need to panic.

F - Avoid

Contains an ingredient Pregnancy Safe recommends avoiding during pregnancy. This may reflect an established risk or a precaution based on limited evidence; check the ingredient guidance and exposure context.

What to do: Do not use during pregnancy. If you've already used it, don't worry - contact your OBGYN if concerned.