Iron is hard on the digestive tract. Constipation is common. Also it can cause nausea, gas and bloating.
If you are taking more than one iron pill per day, I suggest backing down to just one per day for a while. If its still a problem, ask your doctor for a liquid form of iron supplement, such as the brand Feosol. You can then experiment by gradually lowering your dose until you get to a dose that does not cause you constipation.
You can also vary the amount of iron in your pill dose by changing the type of iron salt you are taking. Iron is paired up as a salt with a variety of other ingredients. If you take 300 milligrams (mg) of ferrous sulfate, you will get 60 mg of iron within each dose. If you take 300 mg of ferrous gluconate, you will only have 34 mg of iron in each dose. The ferrous gluconate dose is less constipating for many people. The trade-off is that it replaces your iron more slowly.
Slow-release forms of iron may be less constipating, but they have their downside. The very first part of your intestine (the duodenum and the first part of your jejunum) is where iron is absorbed best. A slowly releasing iron pill can travel past this area before releasing iron, so that you dont ever have a chance to absorb it.
To avoid constipation, drink plenty of fluids and try to be more physically active. If you need fiber, try dietary changes first. Eat more whole grain foods and vegetables such as carrots, cucumbers, zucchini and celery. Take it slow, since these foods often increase intestinal gas.
If you need a fiber supplement, they are safe. But dont take it at the same time you take your iron. When taken at the same time, less iron gets absorbed.
If you are already very constipated, adding more fiber may temporarily make things worse. In that case, call your doctors office for advice.