Serrum ferritin is increasing but at a slow pace after taking iron supplements for 5 monts then why hair fall has started again when it stopped earier?

Cause important: Simple iron deficiency should correct within 3 months of starting replacement. If there is no improvement or a slow response the cause of the iron deficiency matters. If there is ongoing blood loss the improvement will be delayed or absent. How you take iron matters--better absorption on empty stomach but maybe more side effects. Iron malabsorption is a rare possibility. Discuss with your doctor.