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Low hemoglobin is either due to blood loss or the body not being able to form enough blood due to various causes including bone marrow disorders. So, it is better to get her PBS (peripheral blood smear) done.
Meanwhile, in diet and supplements, give her apples, pomegranate, beetroot, green leafy vegetables, and Autrin tablet (Iron, Folic acid, Vitamin B12) once daily.
For more information consult an internal medicine physician online --> https://www.icliniq.com/ask-a-doctor-online/internal-medicine-physician