For improved cognitive function, patients take 1.6 grams of L-arginine once daily for three months at any time, according to Mayo Clinic. If taking L-arginine by mouth for diabetes, the patient should take 3 grams of the amino acid three times a day.
If a patient is taking L-arginine for coronary artery disease, take up to 9 grams by mouth in doses of 3 grams each for up to six months, claims Mayo Clinic. For treating asthma, patients should take a single dose of 50 milligrams of L-arginine per kilogram of body weight once a day. Before treating any condition with L-arginine, a patient needs to speak with a doctor, and never take more than 6,000 milligrams a day.