Lysine is an essential amino acid, which means that you must get the lysine your body needs through your diet.
Many people take lysine supplements to treat cold sores, and evidence suggests that it can help reduce symptoms and prevent outbreaks.
Because it is generally safe, there is no maximum dose for lysine intake.
Lysine for Cold Sore Outbreaks
Lysine is known to inhibit the activity of arginine, an amino acid that promotes the growth of the herpes simplex virus (HSV), the virus that causes cold sores.
A narrative review published in 2023 in Viruses found that taking more than 3 grams of lysine per day helped prevent HSV outbreaks and reduced outbreak symptoms in study participants.
Lysine is generally recognized as safe, though very high doses may cause gastrointestinal symptoms like diarrhea, according to a systematic review published in the Journal of Nutrition.
If you want to take lysine to prevent cold sore outbreaks, researchers recommend taking no more than 6 g per day to avoid adverse side effects.
Is a Lysine Overdose Possible?
Because the side effects of too much lysine are not severe, there is no maximum dose.
However, the Journal of Nutrition review also found that taking more than 6 g per day can cause digestive symptoms like nausea, stomachache, and diarrhea.
Foods Rich in Lysine
If you consume adequate protein in your diet, you'll likely get enough of the amino acids you need, including lysine.
According to the 2020-2025 Dietary Guidelines for Americans, adults should get between 10 and 35 percent of their daily calories from protein.
According to Cleveland Clinic, these foods are particularly rich in essential amino acids:
- Beef
- Fish
- Eggs
- Poultry
- Soy
- Quinoa
- Buckwheat
Because the richest sources of lysine are animal-based foods, consider talking with your doctor or a registered dietitian if you're vegetarian or vegan. They can help ensure that you're getting adequate lysine in your diet.
Safety Precautions
More research is needed to fully understand the effects of lysine supplements. Additionally, the U.S. Food and Drug Administration does not regulate dietary supplements, so the quality of supplement products may vary widely.
Always talk with your doctor or a registered dietician before taking a new dietary supplement. They may recommend alternative treatments if you have other health conditions.
