A haemoglobin level of 12 g/dL is borderline for women. To support your red blood cells, Vitamin B12, Folic Acid (B9), and Vitamin C (which enhances iron absorption) are highly recommended. If iron is prescribed, ?gentle iron? (iron bisglycinate) is the best option to avoid stomach irritation. While no active supplement is entirely free of side effects, these formulations are highly tolerated and rarely cause issues. To prevent mild nausea or constipation, take them with meals and drink plenty of water. Please consult your doctor for the exact dosage suitable for you.