Q. I’m feeling tired all the time. Should I take iron supplements and see if that makes me feel better?

A. Not without seeing your doctor first.

Your body needs iron to produce hemoglobin, the protein molecule in red blood cells that carries oxygen to every part of your body.

When iron levels are low, your cells don’t get the oxygen they need, which can leave you feeling tired. And it’s not uncommon: In the U.S., iron deficiency affects up to one in six older adults, including 16 percent of menstruating women, according to the Centers for Disease Control and Prevention. It also affects 7 percent of children.

“But don’t take iron supplements unless a doctor has recommended them,” says Consumer Reports chief medical adviser Marvin M. Lipman, M.D.

That’s because there are many possible reasons, other than low iron levels, for fatigue. These include disorders that interfere with your sleep (like achy hips and knees or sleep apnea), and conditions that can zap your energy, like hypothyroidism, or even boredom and stress. So your doctor’s first step, Lipman says, should be to take a thorough medical history to look for other health issues that might be making you listless.

If the history doesn’t suggest a reason for your exhaustion, then a blood test makes sense. The test will count your red blood cells. If they are low (a condition called anemia), that’s a good indication that your iron levels are low, too, and your doctor may order a specific iron test.

If that test confirms that you have low iron, it’s important to identify the cause. Low iron levels can be a symptom of health problems, including heavy menstrual bleeding, gastro-intestinal bleeding from an ulcer, or even a cancer. Certain intestinal disorders, such as celiac disease, can also interfere with nutrient absorption and result in iron deficiency.

“Taking iron supplements on your own can boost blood iron levels. That can mask anemia and interfere with the diagnosis of a serious underlying health problem—one that might require immediate attention,” Lipman says.

Iron supplements can also cause side effects such as constipation, nausea, and vomiting.

What you eat (or don’t eat) can also affect iron levels. According to the Institute of Medicine, men need 8 mg per day and women require 18 mg per day until age 50, and then 8 mg per day after their 50th birthday; pregnant women require 27 mg; and nursing moms need 10 mg per day. You’ll get about 8 mg of iron in total, for example, if you eat 2 eggs (2 mg iron), 3 ounces of steak (2 mg iron), 1 cup of broccoli (2 mg iron), and a half cup of kidney beans (2 mg iron).

“If you eat a balanced diet, you should get enough iron from the foods you eat,” says Consumer Reports dietitian Maxine Siegel, R.D. “But if you’re a vegetarian or a vegan, fulfilling that iron requirement can be challenging,” she says.

That’s because the iron in meat, poultry, and fish is better absorbed than the iron from fruit and vegetable sources.

“Eating iron-rich foods, like legumes, with fruits and vegetables that contain vitamin C, such as oranges, broccoli, Brussels sprouts, and tomatoes can boost your body’s ability to absorb iron,” Siegel says.

On the other hand, some foods, including coffee and tea, can block iron absorption.

If your doctor does recommend taking iron supplements, be sure to tell him or her about any other medications you are taking, since iron supplements can interact with certain drugs. For example, iron can hinder the body’s absorption of the thyroid drug levothyroxine (Synthroid and generic), and proton pump inhibitors, such as lansoprazole (Prevacid and generic) and omeprazole (Prilosec and generic), can reduce the amount of iron your body absorbs.

And if you have any young children in the house, be sure to keep all iron supplements well out of reach.