If your ferritin is 13 and you have been anaemic you need a lot more than one Spatone. Were you prescribed ferrous sulphate? That often seems to be badly tolerated. I have used ferrous fumerate, ferrous bisglycinate, Ferrochel.
The ferritin range is set too low for women. You should aim to get up to at least 80 - 90. You can safely take up to 45mg daily iron in your position, but I would take it more slowly - 20mg a day with plennty of vit C. You might find that with these other supplements you have no problems.
The best site I have found is the US site on this aimed at doctors, but it is not difficult to understand.
“Adults with normal intestinal function have very little risk of iron overload from dietary sources of iron . However, acute intakes of more than 20 mg/kg iron from supplements or medicines can lead to gastric upset, constipation, nausea, abdominal pain, vomiting, and faintness, especially if food is not taken at the same time [2,5]. Taking supplements containing 25 mg elemental iron or more can also reduce zinc absorption and plasma zinc concentrations [3,70,71].”
However, it is not dangerous to take 45mg daily if you are adult. (Children are a very different matter, and it is v important to keep iron supps well away from them.)
I cannot emphasise enough how important it is for you to get your iron up. You cannot function properly if your blood lacks enough. And remember (Rushton et al 2010) that the ranges for anemia in women are set lower than in men - without an evidence base of tests of ranges drawn from healthy women !!!!
"Furthermore, 90% of UK females of childbearing age do not achieve the recommended daily intake of elemental iron (14.8 mg) from their diet.9 Evaluation of the haemoglobin concentration and red blood cell count of women from Canada, Central America, China, and the United States shows that this situation is widespread.4,10–14 Women worldwide are at risk of being in a negative iron balance, and by current criteria if their haemoglobin concentration is less than 115 g/l they are deemed to be anaemic, whereas in men the cut-off point is 130 g/l.15"
Do you have any idea why your iron is so low?