All three deficiencies usually travel together, and correcting them properly needs your actual report values, not a generic combo. Broadly,
Vitamin D is corrected with a weekly 60,000 IU sachet course and then a maintenance dose;
B12 either as oral 1500 mcg daily or a short injection course if levels are very low; iron works best as ferrous ascorbate/bisglycinate with vitamin C, on an empty stomach, along with folic acid. Iron and
calcium must not be taken together. If you are also getting heavy periods or persistent fatigue, the cause of the iron loss matters more than the tablet.
Next Steps
Share your actual
vitamin D,
B12, haemoglobin and
ferritin values with me and I will write the exact doses and duration for you. Repeat testing after 3 months. You can book a Practo consult with me and we will plan it in one sitting.