Low Feritin Levels

I’ve had issues with hair loss cause my ferritin was very low. I know that you ferritin levels need to be around 70 for regrowth. I’ve been taking iron supplement and now my levels are currently at 66 and my question is how long does it take for for your hair to regrow again after raising your ferritin levels and what can I do to make sure my ferritin 

It might take a year to see the value of correction