Q: I have iron deficiency anemia. What could have caused it? Also, my doctor wants me to take a daily 325 mg iron sulfate supplement. Is that dangerous? The recommended daily dose of iron is much lower.
A: Most iron in the body is stored in red blood cells. If you don't have enough iron, it can lead to a low red blood cell count. Doctors call this iron-deficiency anemia, and it's more common in women.
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Most people get enough iron in their diet; it is plentiful in a variety of foods, including red meat, chicken liver, lentils, beans and spinach. It's uncommon for a lack of iron in the diet to be the only cause of iron deficiency anemia.
Some people fail to absorb the iron in their food because of digestive problems, such as celiac disease. Certain kinds of stomach or intestinal surgery can also interfere with iron absorption.
Loss of blood is the leading cause of iron deficiency. Normally, red blood cells live about 120 days and then die. But the iron inside them gets transferred to new young red blood cells. In contrast, when people lose blood, they lose a lot of iron.
Heavy menstrual bleeding is a common cause of iron deficiency in women. When I see a premenopausal woman with iron deficiency anemia, iron loss because of menstrual bleeding is the diagnosis that I think is most likely.
But sometimes you can be fooled -- another condition entirely may be the cause.
What other conditions? A doctor always needs to check to see if there is blood loss in the gut or in the urinary tract. Many different gut conditions, including irritation of the wall of the esophagus (the swallowing tube), stomach ulcers, or colon polyps or cancers are always a possibility. These conditions may not produce blood that a person recognizes.
The leaking of blood can be so slow that there is no visual sign of it in a bowel movement. Testing for what is called fecal occult blood can detect blood that is invisible. If that test is positive, further testing of the gastrointestinal tract is necessary.
Conditions such as kidney stones or cancers of the kidney or bladder also can produce a slow leakage of blood into the urine and out of the body. It may be invisible, but examining the urine under a microscope can show the red blood cells.
One of my patients developed iron deficiency anemia because she frequently donated blood. If you're a frequent blood donor, stop donating blood until your iron levels return to normal.
The best supplement to treat iron deficiency anemia is what your doctor recommended, iron sulfate. The dose recommended is fine -- your body needs more than the usual daily dose. Many doctors prescribe an even higher dose: 325 mg of iron sulfate one to three times a day.
Your doctor likely prescribed the lower dose of only one 325 mg tablet per day to decrease the risk of side effects. The most common ones are upset stomach and constipation.
• Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com.