For a male aged 35 cholesterol is normal but triglycerides are 3.77 mmol/l doctor said with exercise and diet it should be fine but can he also take fish oil? if yes how many mg? thanks?

Reduce your intake of saturated fats and lose weight through exercise and diet. Fish oil may or may not be helpful.For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. Get HPV, Flu and Covid vaccines. Wish you good health!