L-Norvaline is an amino acid that does not get built into proteins. It blocks arginase, the enzyme that breaks down arginine. This action is meant to help sustain nitric oxide levels during a workout.
Evidence from human studies is thin. We have little data on whether it works as well as plain L-citrulline, or if it offers any real advantage. Some early lab studies warn that blocking arginase might lead to ammonia accumulation, which could stress blood vessels and nerves over time.
Users typically take it 30 to 60 minutes before exercise. Reliable information on proper dose, absorption, and long-term safety is still missing.