What is lysine?
Lysine is an essential amino acid. That means it's a building block of protein your body can't make on its own, so you have to get it from food.
Your immune cells use it to do their job, so it's sometimes called the "immune amino acid." When you're low on it, you're known to be more prone to cold sores (blisters around the lips caused by herpes simplex).
Who lysine may help
- □ You often get cold sores on your lips when you're run down
- □ You feel like your immune system is weak
- □ You take arginine (an amino acid used for blood flow and exercise)
People who take arginine often add lysine for balance. The two amino acids compete for the same absorption sites in the body, so lysine is commonly taken alongside arginine as a supporting supplement.
Lysine dose and kidney side effects
Bottom line: 500–1,000 mg a day causes almost no problems. Side effects are generally uncommon.
| Daily dose | Verdict |
|---|---|
| 500–1,000 mg | Safe for most people |
| 2,000–3,000 mg for a long time | Use caution. There's no real reason to take this much |
Here's why to be careful. A woman in her 40s who took 3,000 mg a day for 5 years developed kidney damage serious enough to need dialysis. She had both a condition where the kidneys can't reabsorb nutrients properly (Fanconi syndrome) and kidney inflammation.
This isn't common. But it's best to avoid taking high doses for years.
- If you have kidney problems, avoid high-dose products and talk to your doctor first.
- One 1,000 mg tablet is enough. Don't take several hoping for a bigger effect.
Medications and conditions to watch
- Check Kidney disease treatment — High doses strain the kidneys — talk to your doctor before taking
Combinations
Works well with: Propolis, L-Arginine
Frequently asked questions
Can I take lysine for cold sores?
Yes. Low lysine makes cold sores more likely, so many people who get them often take it. 500–1,000 mg a day is enough, and some people take it with propolis.
What's the maximum amount of lysine I can take per day?
500–1,000 mg a day causes almost no problems. Taking 2,000–3,000 mg for a long time may strain your kidneys, so it's best avoided.
Is lysine bad for your kidneys?
It's fine at normal doses. But in one case, a person's kidneys were badly damaged after taking 3,000 mg a day for 5 years. If your kidneys are weak, talk to your doctor first.
Can I take arginine and lysine together?
Yes. People who take arginine sometimes add lysine to keep things balanced. Stick to normal doses of both.
Related concerns
Last updated 2026-10-12