Found out I was anaemic and had very low ferritin levels (5) in 2018. Had a 2 week course of iron tablets, also improved my diet massively and it climbed to the dizzy heights of 7 
Am now on a 3 month course of iron tablets at a much higher dose (320mg). My blood count is now normal but presume my iron stores are still lowish as I believe the tablets take a while to kick in. Starting to feel so much better now, I just didn’t realise how tired and under the weather I’d been feeling, palpitations, tiny bit more short of breath, even depressed and having funny anxiety attacks which I’ve never been prone to. Out of interest just wondered what symptoms others had experienced as I probably would never have known if I’d not had blood taken ?