A lab test can help determine if you’re dealing with a deficiency, in which case supplements can be incredibly helpful and even necessary. Low iron levels can be tied to a number of factors: You may not be consuming enough through food sources; you might have an increase in need (due to pregnancy or a chronic condition like anemia); or your body just isn’t absorbing it well.

Loss of blood can also contribute to anemia (such as during menstruation or during a surgery), says Cording. In this case, an iron supplement may be warranted for a short period of time to replenish stores.

“Anyone with a heavy period, pregnant people, infants, frequent blood donors, athletes (especially female athletes), and people with cancer, gastrointestinal disorders, or heart failure are more likely to be low in iron, making them good candidates for iron supplements,” says Moon.

She also notes that it’s not a bad idea for all women of childbearing age to assess their iron status to see if a supplement is right for them.

Dietary choices can play a role in iron levels, too. “Vegetarians and vegans rely on plant-based iron, which isn’t absorbed as efficiently as the iron in meat,” says Agyeman. “That doesn’t mean you can’t get enough, it just takes a bit of strategy.” Think: eating more beans, lentils, tofu, leafy greens, quinoa, pumpkin seeds, and fortified grains—and, of course, considering an iron supplement to help bridge the gap.

As for people who absolutely should not take iron supplements: “There’s an inherited condition called hemochromatosis where iron builds up to toxic levels that can cause liver cirrhosis, liver cancer, and heart disease,” says Moon. “These folks should avoid iron and vitamin C supplements, and follow the guidance of their health care team.”