L-Ornithine is a non-proteinogenic amino acid your body makes naturally. The isolated 'L-' form helps the liver clear ammonia, a waste product from protein metabolism, through the urea cycle. Unlike related forms such as ornithine alpha-ketoglutarate, L-Ornithine targets ammonia clearance directly. People typically use it to ease post-exercise fatigue or to support sleep.
Many take it before a workout to reduce ammonia buildup that accumulates during hard physical effort. This action often cuts feelings of fatigue and speeds recovery. Others use it 30 to 60 minutes before bedtime. The supplement can prompt a small release of growth hormone, which may help the body relax and improve sleep quality.
Take L-Ornithine on an empty stomach to get the best absorption. High doses sometimes cause mild stomach upset. Anyone with a kidney or liver condition should speak with a doctor first, since the amino acid influences how the body handles nitrogen.