I hope you informed your doctor before taking iron. Iron toxicity caused by over-ingestion of iron supplements is the number one cause of death by poisoning in children, and it is still very dangerous for adults.
No, they need to specifically check iron levels. You could be doing damage taking it if you don’t need it. Definitely let your doctor know and ask for a level check.
I wouldn’t consider the black stools and constipation a necessarily bad thing. That is completely common with iron supplements even if you really do need them.
The amount of iron ingested may give a clue to potential toxicity. The therapeutic dose for iron deficiency anemia is 3–6 mg/kg/day. Toxic effects begin to occur at doses above 10–20 mg/kg of elemental iron. Ingestions of more than 50 mg/kg of elemental iron are associated with severe toxicity.[9]
A 325-mg tablet of ferrous sulfate heptahydrate has 65 mg (20%) of elemental iron
I was told that was a reason to stop the supplements. My family all have a blood disorder that makes us unable to absorb iron properly, and we have taken iron supplements before when we had a doctor who was not well versed in our disorder. The problem with our type of anemia is that we still get the proper amount of iron in our blood, but it does not absorb into the red blood cells so it just floats freely in our system. This means we are more likely to die of iron toxicity if we take supplements, since the iron doesn’t go anywhere.
Then they probably didn’t check your iron. I think you should ask your doctor about your iron if you are concerned, rather than trying to fix a problem you might not have on your own. Some foods high in iron are spinach, steak, and broccoli. Eating more of those foods might be all you need.