Best Lysine Supplements

While choosing our top picks for lysine supplements, we focused on four main criteria: safety, cost, quality, and customer satisfaction. See how our top brands fared to help determine which product may be best for you.

Winner: Thorne

Quality is a top priority when researching and testing products, and we assess quality by asking ourselves several questions: How are the ingredients sourced? How effective is a given supplement? Does the company offer a customer satisfaction guarantee?

Thorne L-Lysine 500mg won our quality assessment as it adds leucine to help manage whole-body amino acid metabolism and improve muscle development. The combination of L-lysine and L-leucine aids in faster recovery and prevents age-related muscle atrophy.

Thorne’s lysine supplement is also one of the more effortless products to swallow, as their lower dosage enables smaller capsule sizes. Thorne Research is a highly reputable and trusted brand, providing a 60-day money-back guarantee, ingredient transparency, and free ground shipping on all orders in the U.S.

Winner: Life Extension

Our top supplements should be affordable without sacrificing quality or safety. Next to quality, we look at a product’s cost-effectiveness compared to other brands, alongside comparisons of shipping costs, subscription or bulk discounts, and other ways to save.

Life Extension L-Lysine 620mg is a clear winner for affordability, priced at just $0.07 per serving. The company offers two other ways to earn savings: enrolling in the subscription auto-ship membership plan or purchasing in bulk (buying four or more products as a single order).

Life Extension also provides a one-year customer satisfaction guarantee, so you’re never at risk of throwing money down the drain if it doesn’t work for you. It also offers free shipping on all subscription orders and single purchases over $50. Shipping costs start at $5.50 for a single purchase of one bottle of capsules without a subscription.

Winner: NOW

Whether you’re a healthy adult or suffer from chronic illness, it’s essential to carefully assess supplements to determine whether they’re safe for you. The FDA doesn’t regulate supplements in the same way it does food or prescription medication, leaving the bulk of the work in your (and our) hands. To evaluate a product’s safety, we look at several factors, including:

• Ingredient transparency
• Lack of food allergens
• Manufacturing methods
• Fillers and additives
• Third-party testing

Our winner for safety is NOW L-Lysine 1,000mg. NOW Foods is third-party tested and certified by Underwriters Laboratories (UL). The company manufactures L-Lysine 1,000mg under Current Good Manufacturing Practices (cGMP) and includes no GMOs or common allergens including gluten, nuts, and soy. It is kosher, halal, and vegan-friendly, and NOW Foods ensures that its manufacturing methods are environmentally sustainable with a low carbon footprint.

Winner: Life Extension

We all want the most effective, safe, and affordable products. But if a product doesn’t work for you or causes adverse side effects or allergic reactions, it’s reassuring to know that you can quickly and efficiently get a full refund.

We chose Life Extension L-Lysine 620mg as our winner for customer service and satisfaction based on its lengthy one-year satisfaction guarantee and free shipping provided on subscription orders and orders over $50. L-Lysine 620mg also offers more ways to save on purchases than other brands, and all products come with a Certificate of Analysis to ensure quality.

In the chart below, you’ll see how our favorite brands compare regarding customer satisfaction, quality assurance, cost, and available discounts. The product that works best for you will depend on your budget, dietary needs, and health goals.

Cost comparisons in the chart below reflect single purchases and don’t account for savings based on subscription plans or bulk purchases.

Lysine is an essential amino acid that helps us build protein. Our bodies can’t create essential amino acids, so we need to attain them through diet or supplementation for proper functioning. Lysine also has some anti-inflammatory and anticonvulsant effects. It boosts immunity and aids in treating wounds, cold sores, and genital herpes.

Lysine occurs naturally in several foods, including:

Lysine is an excellent supplement choice for many individuals with a broad range of health benefits, including:

Vegetarians and vegans often benefit significantly from lysine supplements because their diets do not contain as many high-protein foods, aside from legumes.

Amino acids are the building blocks of protein and contribute to many critical bodily processes, including cell generation and carnitine production. Carnitine converts fatty acids into energy, lowering cholesterol levels in the body.

Lysine also helps the body synthesize collagen and reduces outbreaks of cold sores and genital herpes. It aids in anxiety reduction by blocking stress response receptors (cortisol) in the body.

When combined with calcium at lower dosages, lysine can prevent and treat osteoporosis by enhancing calcium absorption and improving its renal conservation. The enhanced collagen production of lysine assists in healing wounds and increasing cell growth.

Scientific studies have shown that lysine supplementation can help manage heart disease by preventing lipoprotein from binding to arterial walls, resulting in fewer plaque deposits and pressure buildup in the arteries.

Lysine’s ability to prevent and treat herpes simplex virus (HSV) I and II by slowing down the body’s production of arginine carries over to treating shingles and other viruses. It helps to regulate immune cell responses, block apoptosis, and promote cell proliferation.

Lysine supplements are generally well tolerated by healthy adults. However, those with kidney, liver, or gallbladder issues should avoid lysine because it can cause gallstones, renal dysfunction, and failure.

Individuals taking medications or suffering from chronic illness should consult with a physician before taking lysine, as it can interfere with calcium supplements and gastrointestinal medicines. High dosages — such as those used for cold sores, herpes, or shingles — should not be continued past 48 hours without medical supervision.

Lysine can cause side effects, particularly in higher doses. These include:

• Nausea
• Stomach pain
• Diarrhea
• Gallstones
• Renal dysfunction or failure
• Increased calcium absorption

When we tested lysine supplements, some of our testers experienced several benefits in the first one to two weeks, including:

• Reduced anxiety
• Improved performance at the gym
• Boosted energy
• More endurance
• Better sleep

When used over an extended period of time, we experienced minor weight loss, less joint pain, and better hair, skin, and nail health. Additionally, testers who experienced frequent cold sores were pleased with fast results when taking high doses for 48 hours.

When taking high doses of lysine to treat cold sores, genital herpes, or shingles, you’re likely to experience relief within 48 hours. Boosted endurance, energy, and athletic performance may appear within two to three weeks of starting a lysine regimen. Most achieve bone, skin, hair, and nail health improvements within one to two months of daily supplementation.

Best overall

Thorne L-Lysine 500mg was our overall winner based on several factors. The added leucine in this product helps manage whole-body amino acid metabolism, promoting more effective muscle building and lowering average blood sugar. These complementary amino acids enhance faster recovery and slow muscle atrophy associated with aging. Additionally, the small dose in each capsule allows for more dosing flexibility and a smaller size, which makes them easier to swallow too.

This gluten-, soy-, and dairy-free supplement comes with free ground shipping on orders in the U.S. and a 60-day satisfaction guarantee.

Each capsule of Thorne L-Lysine 500mg contains 500mg L-lysine monohydrochloride along with the following ingredients:

• Leucine
• Hypromellose
• Calcium laureate
• Silicon dioxide

Thorne Research promises several benefits for its lysine supplement, including:

• Supports wound healing
• Aids recovery from broken bones
• Maintains healthy gum and lip tissues
• Boosts immunity
• Promotes skin, bone, hair, and nail health

Thorne Research offers an auto-ship subscription membership that takes 10% off purchases and 20% off when you subscribe to three or more products.

Thorne Research provides free ground shipping on all orders in the contiguous U.S.

Runner-up overall and best for vegans

NOW L-Lysine 1,000mg won runner-up overall and best for vegans based on its quality, good manufacturing practices, and flexibility with several diet limitations. This kosher supplement is halal- and vegan-friendly and contains no common allergens like soy, wheat, gluten, eggs, milk, tree nuts, fish, or shellfish. NOW Foods is a trusted, family-owned brand dating back to 1968 with a commitment to quality testing and affordability.

NOW L-Lysine 1,000mg provides 1g of lysine with the following additional ingredients:

• Microcrystalline cellulose
• Silicon dioxide
• Stearic acid (vegetable source)
• Vegetarian coating
• Croscarmellose sodium
• Magnesium stearate (vegetable source)

With double the dosage of lysine than the regular NOW L-Lysine supplement, this product is more effective at treating cold sores, genital herpes, and shingles (which need doses of about 3g). The high dose boasts the following additional benefits:

• Promotes collagen and elastin synthesis
• Boosts immunity
• Improves skin, tendon, and bone health
• Promotes carnitine production to boost fat burning
• Increases energy and endurance
• Aids healthy cardiovascular function

NOW Foods does not have a subscription savings plan, but ordering in bulk means you’ll save more. There are two size bottles you can choose from:

• 100 tablets: $10.39
• 250 tablets: $22.39

Shipping and handling fees start at $6.95, but NOW Foods provides free shipping on all orders over $50.

Best budget pick

Life Extension L-Lysine 620mg is a clear winner for affordability at just $0.07 per serving, and the company does not sacrifice quality for low pricing. Life Extension provides a Certificate of Analysis with each supplement purchased, so you’ll know that they’ve thoroughly and safely tested each supplement. The manufacturer offers two avenues for savings: auto-ship subscription membership and bulk purchases. Like Thorne L-Lysine, Life Extension L-Lysine 620mg contains added L-leucine, a complementary amino acid.

Life Extension provides a one-year 100% money-back guarantee on all products.

Life Extension L-Lysine 620mg provides 620mg of L-lysine (as L-lysine HCl) as well as:

• Vegetable cellulose (capsule)
• Vegetable stearate
• L-leucine

Life Extension L-Lysine 620mg provides the following benefits:

• Promotes healthy nitrogen balance
• Reduces cortisol levels, alleviating anxiety and stress
• Inhibits glycation, reducing signs of aging
• Supports healthy calcium metabolism
• Improves bone, joint, skin, hair, and nail health

Life Extension provides a subscription membership that reduces the cost of L-Lysine 620mg by 11% and bulk savings of 11% on single purchases of four or more units. These discounts cannot be combined. This means that your purchasing options are:

• Single one-time order: $6.75
• Bulk order or subscription: $6

Standard shipping starts at $5.50 for orders under $50. Orders over $50 and subscription orders receive free standard shipping.

Best for cold sores

Nature Made L-Lysine 1,000mg was our pick for the best supplement for cold sores based on its high dose per capsule. Nature Made is a trusted, affordable brand, and its products are widely available from online retailers, pharmacies, and big box stores. This gluten- and additive-free supplement contains no artificial flavors and provides transparency regarding its ingredient amounts.

You can earn savings by enrolling in the company’s subscription membership. Shipping is free on orders over $25.

Nature Made L-Lysine 1,000mg provides 1g of L-lysine (as lysine hydrochloride) and the following additional ingredients:

• Cellulose gel
• Hypromellose
• Stearic acid
• Silicon dioxide
• Magnesium stearate
• Croscarmellose sodium
• Polyethylene glycol

Nature Made L-Lysine 1,000mg provides the following health benefits:

• Supports protein synthesis
• Effective in treating cold sores, genital herpes, and shingles
• Enhances bone, joint, nail, hair, and skin health
• Reduces anxiety and stress
• May effectively treat schizophrenia symptoms

Nature Made L-Lysine 1,000mg is affordable and contains a higher dosage than many brands. The company offers a subscription savings membership that reduces prices by 10%. A single 60-capsule bottle costs $8.99, and you can save 90 cents by joining their subscription program (dropping the price to $8.09).

Nature Made provides free shipping on orders over $25. For orders below $25, shipping starts at $8.

Best for those with allergies

Superior Labs L-Lysine 500mg is one of the purest lysine supplements on the market, emphasizing its lack of fillers, common allergens, heavy metals, and pesticides. It is non-GMO, vegetarian-friendly, and manufactured in a GMP-certified facility in the U.S. We appreciate Superior Labs’ transparency in ingredient labeling and its fermentation process in manufacturing.

Superior Labs L-Lysine 500mg provides 500mg of L-lysine (as L-lysine hydrochloride) along with:

• Plant cellulose (vegetable capsule)
• Organic rice concentrate

The L-lysine capsules provide the following health benefits:

• Promotes mental well-being and reduces anxiety
• Supports immunity
• Aids in calcium absorption
• Helps maintain muscle mass
• Promotes cell growth and strength
• Maintains healthy bones and joints

Superior Labs offers an auto-ship subscription program that reduces the costs of products by 5%. While the savings is not significant, it adds up when purchasing refills over time.

• Single order (120 capsules): $18.45
• Subscription order (120 capsules): $17.53

Superior Labs provides free shipping on orders over $45. For orders under $45, shipping rates start at $4.

How much lysine can I take?

Studies have shown you can take up to 3,000mg of lysine for one year without toxic effects. Those taking high doses to treat HSV I or II generally only need lysine supplementation for 48 hours. However, you may experience adverse gastrointestinal side effects in higher dosages, including nausea, stomach pain, and diarrhea. Other side effects include kidney issues and gallstones.

What medications don’t work well with lysine supplements?

If you are taking any ongoing medication or have chronic health issues, you should consult with your doctor before adding lysine or any dietary supplement to your regimen. Lysine supplements can interfere with gastrointestinal medications and calcium supplements.

When should I take lysine supplements?

We recommend taking lysine supplements in the morning, before your morning coffee, so that they have the most time to digest. However, you can take them at any time of day, with or without food.

What is the difference between lysine and L-lysine?

Lysine is a primary amino acid and essential nutrient for vertebrates. L-lysine is the biologically active form of lysine that is found in supplements.

Can lysine damage my kidneys?

You should not take lysine supplements if you suffer from kidney issues. In animal studies, researchers have shown that high doses of lysine supplements can cause acute renal failure.

How does lysine affect hair growth?

Lysine is an essential amino acid that can prevent hair loss and promote growth. Sudden, unexplained hair loss is a sign you might be experiencing a lysine deficiency.

Do lysine supplements help heal cold sores?

In higher dosages (3g per day), lysine effectively improves cold sores and genital herpes. However, you should not take high dosages for long periods, and individuals with gallbladder or cardiovascular disease, immune dysfunction, or asthma face particular risks taking lysine. You should consult with your doctor before integrating lysine into your daily regimen.

Can lysine help me lose weight?

Yes. It won’t cause your pounds to melt away, but lysine aids weight loss by helping the body produce carnitine, which converts fatty acids to energy. It also boosts energy levels and physical endurance, giving you the capability for longer, more effective workouts. Lysine promotes lean body mass development and muscle strength.

What effects does lysine have on blood pressure?

Lysine supplementation may help lower blood pressure in individuals with hypertension. However, you should talk with your doctor before adding lysine to your daily regimen, as it can interact with several medications and supplements.

How long will it take until I see results from lysine supplements?

If taking lysine supplements for cold sores or genital herpes, you should see results in one to two days. When taken at lower dosages, lysine is likely to affect your energy levels, mood, and weight within one to two weeks of taking the supplement daily.

Can I get lysine from my diet?

Yes. Many foods contain lysine, particularly protein-rich foods such as meat, poultry, eggs, tofu, cheese, and fish. Lysine supplements are particularly effective for vegetarians and vegans, who obtain less lysine from their daily diets. Most people get enough lysine through their diet alone.

Can lysine help soothe joint pain?

As an anti-inflammatory essential amino acid, lysine aids the body in building protein, strengthening joints, and reducing joint pain. It also enhances physical performance among athletes, individuals hitting the gym, and those trying to lose weight.

How does lysine affect mental health?

In double-blind, placebo-controlled studies, researchers have shown that when combined with arginine, lysine can reduce chronic anxiety and lower cortisol levels in the body.

What side effects do lysine supplements have?

The most common side effects of lysine supplementation are gastrointestinal issues (pain, diarrhea, nausea) and an increased risk for gallstones and kidney issues.

Over the past two decades, Innerbody Research has helped tens of millions of readers make more informed decisions involving staying healthy and living healthier lifestyles.

We extensively test each health service or product we review. We try our best to give you, our readers, an unbiased exploration of at-home health options, free of marketing jargon or gimmicks. We evaluate products and services based on their adherence to quality, the latest medical evidence and health standards, and a simple question: would we buy the product or service ourselves if it weren’t part of our job, and would we recommend it to family and friends?

Additionally, like all health-related content on this website, this guide was thoroughly vetted by one or more members of our Medical Review Board for accuracy.