Iron deficiency occurs in two stages. During the first stage, your body gradually depletes stored iron. During the second stage, not enough iron is available for the production of red blood cells, so you become anemic. Red blood cells use iron to ferry oxygen around the body. When red blood cells become deficient in iron, your heart must pump more frequently to make up for the reduced oxygen “cargo” carried by red blood cells.
Your heart normally beats 60 to 100 times per minute when you are at rest. Mayo Clinic physical medicine and rehabilitation specialist Dr. Edward Laskowski says athletes often have lower resting heart rates -- about 40 beats per minute. When you become iron deficient, your heart rate typically increases. However, the broad range of “normal” heart rates and the many factors that influence your heart rate at any given time -- such as physical exertion, emotional state and whether you're standing or sitting -- makes it difficult to diagnose increased heart rate due to iron deficiency. In some cases, you or your doctor may recognize an increase from your previous baseline.
Other symptoms of iron deficiency often accompany increased heart rate. You may notice that your skin seems pale, your nails have become brittle or spoon-shaped, the whites of your eyes have acquired a blue tint, and your tongue feels swollen. You may notice other changes, such as increased fatigue, irritability, headaches, shortness of breath, muscle weakness, decreased exercise tolerance or taste changes.
If you suspect that your heart rate has increased due to iron deficiency, see your doctor. A blood test for hemoglobin, hematocrit and ferritin can confirm whether you are iron deficient. Other types of anemia may also contribute to increased heart rate. Additional blood tests may be required to diagnose anemia due to B-12, folate, B-6 or other deficiencies. Sometimes, your body has enough iron and other nutrients to make new red blood cells, but chronic diseases or other medical problems render it unable to use these raw materials.
If your doctor confirms that your heart rate has increased due to iron deficiency, he may recommend oral iron supplements to correct the deficiency. Other nutrients and medications can interfere with your ability to absorb oral iron, so follow your doctor’s instructions for taking iron supplements very carefully. Oral iron supplements do not work for some people -- especially those with gastrointestinal problems such as inflammatory bowel disease. These people require intravenous or intramuscular iron injections to correct deficiencies.
You should start to feel better a few days after you begin taking iron. Your heart rate may not return to normal for two months, which is approximately the amount of time it takes for hematocrit and hemoglobin to return to normal. Your doctor may order a repeat blood test to confirm that iron supplements are working. She may tell you to continue taking them for six months to one year, to fully replenish your body’s iron stores. If the cause of your iron deficiency is ongoing -- such as heavy menstrual periods, vegetarian diet or antacid use -- you may need to take small amounts of supplemental iron for the rest of your life.
Increased heart rate means your heart is working harder than normal. If your heart is already unhealthy, this can put you over the edge. If you experience chest pain, loss of consciousness, difficulty breathing or swelling in your legs, contact your doctor or go to the emergency room because these are signs of serious heart problems.