Lysine is an amino acid essential to human life. It can be obtained by eating animal protein, eggs, dairy products and beans. If you do not eat much of these foods, you may need to take supplemental lysine, which is often available in the form of L-lysine. L-lysine is generally thought to be safe, but it can be dangerous if you have certain conditions. You should always speak to your doctor before starting supplementation with lysine to avoid potentially problematic conditions and drug interactions.
High doses of lysine have been found to cause gallstones. Lysine can increase your cholesterol. The increase in cholesterol can cause the bile in your gallbladder to retain excessive amounts of cholesterol, which can lead to stone formation. Take caution in using lysine if you have a history of gallstones or if your cholesterol is already high. Gallstones may not cause any symptoms. If they do, you will typically experience nausea, upper right-sided abdominal pain, vomiting and fever. If you develop gallstones, you may need to have your gallbladder removed.
Taking lysine can increase your risk of developing hypercalcemia, abnormally high levels of calcium in the blood. This is especially true if you already take in a significant amount of calcium each day or if you have decreased kidney function. Lysine has been shown to increase the amount of calcium your intestines absorb, according to a review published in the November-December 1992 issue of "Nutrition." To decrease this risk, do not take lysine with a calcium supplement or with dairy products unless you're instructed to do so by your doctor. Consult your doctor immediately if you experience nausea, vomiting, flank or bone pain, muscle weakness or memory loss, as these are symptoms of hypercalcemia.
Lysine has been linked to kidney failure, so do not take it if you have impaired kidney function. Large doses of lysine and other amino acids may induce acute kidney failure even in healthy individuals, according to a review published in the June 2007 issue of "The Journal of Nutrition." Symptoms of acute kidney failure may include pain between the hip and ribs, a decrease in the amount of urine you're excreting, intractable nausea and vomiting, and bloody stools. Seek immediate help if you develop these symptoms while taking lysine.
Pregnancy and Breastfeeding
L-lysine is not recommended for use in pregnant or breastfeeding women because it has not been proven safe in this population. Furthermore, pregnancy can affect the way your kidneys reabsorb it. Do not take lysine if you are pregnant unless your doctor permits it.