Dear Sir: I highly suggest you make an appt. with a Dietitian in India to review your diet as there are foods and vitamins you should not be taking with your genetic disease that affects carbohydrate metabolism and may cause hemolytic anemia. You ask about a B 12 supplement. Lets start with the things to avoid to help your blood - fava bean, sufonamide antibiotics, vitamin C, possibly vitamin K. many other vitamins are suggested and even encouraged. Vitamin E in the range of 400 - 800 IU may be protective against your illness. Daily oral doses of 1000-2000 MCG/DAY OR INJECTION and it is imperative if you are deficient to become repleted as B12 deficiency prolonged can cause bone marrow failure. Also there are other foods to avoid, but I would feel more comfortable if you had a complete assessment and meal plan by an Indian dietitian either by video (telehealth) or walk-in. Best wishes to your health.