There is no generally valid statement on how much isoleucine should be taken in per day. However, the following formula has become accepted in science: 20 mg of isoleucine per kilogram of body weight should be consumed per day(6). Other studies speak of 10 to 20 grams of BCAA per day.(7, 8, 9)
The best way to determine the exact amount is to talk to your fitness coach or get advice from a pharmacy or your family doctor. Especially if you have a deficiency or are on a diet, it is worthwhile to determine the exact dosage.