L-lysine is used to treat and prevent herpes infections and cold sores, according to Drugs.com. L-lysine may also increase muscle mass, help with anxiety, reduce glucose levels and increase absorption of calcium in the intestines.
Some people use l-lysine to reduce pain and toxicity in the body after taking heroin. Research suggests that it may be effective for treating migraine headaches and other painful conditions, although there is limited confirmed information. Some people take l-lysine to improve athletic performance. Studies suggest it may reduce anxiety in males and stress in females, explains WebMD.
Pregnant or nursing women should not take l-lysine unless directed by a physician. Before taking l-lysine, people with kidney problems should speak to a health care professional. Taking l-lysine with calcium supplements may increase calcium absorption, so people with osteoporosis or other calcium-related conditions should talk to a doctor before taking it. Children who are intolerant to lysinuric protein should avoid l-lysine unless directed by a physician, as it may cause stomach cramps or diarrhea, states WebMD.
People with too much lysine in the blood or urine should not take l-lysine. Unless directed by a doctor, people with kidney or liver problems should also not take it. Some people have experienced stomach pain, nausea and diarrhea after taking l-lysine, notes Drugs.com.