Iron tablets can cause stomach problems, but you should not have to guess how to change treatment. Nausea, constipation and diarrhoea are recognised side effects. Contact the prescriber if they prevent you taking the treatment.
Check what you actually take
Write down the product name, strength and prescribed dose. An ordinary dietary supplement is not automatically equivalent to medicine for confirmed iron deficiency. Do not take extra tablets to try to improve a result faster.
Other medicines can affect iron absorption or need to be taken at a different time. Ask a pharmacist about your particular products. Follow the product instructions and take tablets with fluid; ask for advice if swallowing them is difficult.
Make the problem clear
| Problem | Question |
|---|---|
| Nausea or abdominal discomfort | Should timing, taking it with food or the treatment schedule be adjusted? |
| Constipation | Which relief is suitable alongside my treatment? |
| Missed doses | How should I continue without doubling doses myself? |
| Little improvement | Do the diagnosis, absorption, blood loss or treatment need review? |
How is the response checked?
For iron-deficiency anaemia, healthcare staff monitor measures including haemoglobin, or Hb. Iron stores may still need replenishment after Hb improves. Agree on the blood-test plan and treatment duration with your prescriber, considering both symptoms and results.
If improvement does not occur, the reason needs assessment. Simply taking more tablets does not explain why a result has stopped changing. Also ask whether the cause of the deficiency has been investigated, rather than treating the laboratory number alone.
Are there alternatives?
Other treatment routes exist when tablets are ineffective or unsuitable. A clinician decides whether intravenous iron, for example, is appropriate. It is not a routine first choice for every person with fatigue or one low result.
When to get urgent help
Vomiting blood, substantial bleeding or black tarry stool with dizziness or weakness needs emergency assessment. Do not assume serious new symptoms are only side effects. Keep iron out of children’s reach; overdose can be dangerous. In an acute suspected poisoning in Sweden, call 112 and ask for Giftinformation, the poison information service.
Sources and further reading
- 1177: Brist på järn (in Swedish)
- 1177 för vårdpersonal: Anemi (in Swedish)
- Giftinformationscentralen: Järntabletter (in Swedish)
- 1177: Magsår (in Swedish)
Sources and links checked on 22 October 2026. Editorial team: Hagakliniken. General information; individual assessment may differ.