The exact dose that is safe for a cat depends on the individual cat and its health status. However, a general guideline is to give no more than 1 mg of vitamin B1 (thiamine), 2 mg of vitamin B2 (riboflavin), 5 mg of vitamin B3 (niacin), 1 mg of vitamin B6 (pyridoxine), 50 mcg of vitamin B9 (folic acid), and 25 mcg of vitamin B12 (cobalamin) per day.
When considering giving a vitamin supplement, it is essential to consult a veterinarian to determine the correct dosage and to identify if there are any potentially harmful drug interactions.