My low Hb (98) was caused by some form of Iron Deficiency, confirmed by hospital blood test. My blood Iron level was close to zero! Plenty in my red blood cells, but not enough to help with their regeneration in my bone marrow.
I was given two top up boosts of Iron in hospital, iv drip.
My Haemoglobin shot up after this to normal levels (140). You can get kits on Amazon to measure your Hb by pricking your finger. I would though stress to go by what your hospital blood test results are, and use the home kit to monitor whether your Hb is going up or down.
I also take a daily iron supplement tablet to try to ensure my Iron does not get too low again. I found the hospital tablets had an adverse effect with my bowel movements, but they warn you of this. Its the high amount of iron in each tablet, 200 mg. I’ve since found 40 mg tablets that I don’t seem to have any side effects with.