Heme iron supplements are more efficient and better tolerated than the synthetic supplements.
There are no known side-effects to heme iron. Heme iron not absorbed is completely inert and will not cause disturbancies.
The regular non-heme chemical/synthetic supplements will give intolerable side-effects sooner or later that stops the essential therapy. The remaining way is to give iron intravenously as a last resort. This is effective, but has several drawbacks. Intravenous iron therapy is uncomfortable, even painful. It is expensive and needs clinical care. There is a risk of overdose and oxidative stress. The latter is serious and potentially life-threatening in weak patients.
Heme iron supplements can be taken one or two tablets at any time of day and regardless of other food, drink or medication. Tolerance and efficacy will remain high also over longer time.