If you’re feeling lethargic and tired all the time, most GPs will recommend that you have an iron test. And if you’re one of the 8% of women in the UK diagnosed with anaemia, they’ll prescribe you high-dose iron tablets. Within a few days, you might start to feel significantly more energetic. But… well, there’s a downside: the side effects.

Prescription iron supplements are known for triggering some unpleasant side effects, especially when it comes to the digestive system. These side effects include tummy pain, constipation, diarrhoea, nausea and black poo – the latter of which can be especially alarming when you first notice it.

The NHS says it’s important to keep taking prescribed iron tablets even if you get side effects, but they can be disruptive. So, why do these side effects happen in the first place? And is there any way to minimise or avoid them altogether? We asked an expert.

Iron supplements messing with your stomach? Here’s why (and what you can do about it)