Generally, arginine is considered safe for humans, but because it promotes nitric oxide production, and this relaxes blood vessels, hypotension (low blood pressure) could result from too much arginine.
Side-effects are rare and mild but some people can experience abdominal pain, bloating, diarrhoea or gout.
If you suffer from cold sores you should minimise your arginine intake. The Herpes simplex virus that causes cold sores needs a lot of arginine to replicate. Conversely, the amino acid lysine inhibits viral replication. A diet low in arginine and high in lysine may help prevent or treat herpes outbreaks.
Generally, arginine seems to be well tolerated at doses below 30mg daily, but if you are looking at supplementing with this amino acid at any quantity above a few grams daily in addition to food, seek the advice of your healthcare professional.
Around 9g a day seems to be useful in coronary artery disease, 5g daily for men with erectile dysfunction if abnormal nitric oxide metabolism is their issue, and around 12g a day for people with angina, although the evidence remains uncertain. Human doses to achieve improved blood-sugar metabolism are yet to be established.