How to Take Iron Supplements

After a short hospital stay for a bleeding ulcer, 78-year-old Mabel became anemic. She was discharged home on medicine to heal her ulcer, plus an iron supplement. Despite taking iron for 3 months, Mabel’s blood tests showed she was still low in iron.

When I asked her which iron supplement she was taking, she proudly showed me a bottle of ferrous gluconate 300mg sustained-release capsules instead of the ferrous sulfate tablets originally prescribed.

"The iron tablets they gave me at the hospital really upset my stomach, so the pharmacist recommended this one instead. Besides, those doctors tried to give me a sulfa drug, and I'm allergic to sulfa!" she exclaimed. I explained that ferrous sulfate was very different from a sulfa drug, and she could take it safely. 

Iron supplements have been used in medicine since ancient times. Greek physicians treated people who were pale and tired with drinking water enriched with iron. They created iron-rich water by leaving swords in water to rust or reused the water that blacksmiths used to cool hot iron.

Iron is a critical part of hemoglobin, a protein responsible for carrying oxygen throughout the body. Your body needs four iron atoms to make each molecule of hemoglobin, which also gives blood its distinctive red color. Without enough iron available to make hemoglobin, your blood carries less oxygen, and you become pale and tired.

The most common cause of iron deficiency is blood loss. You can lose blood from stomach bleeding like Mabel, heavy menstrual periods, or from your intestines through ulcers, hemorrhoids, or diverticulitis. You can be low on iron from a poor diet, gastric bypass surgery, kidney disease, or simply need more iron during pregnancy or breastfeeding. 

Iron deficiency anemia is treated with iron supplements which provide iron for hemoglobin in your blood and replenish iron stores in your bone marrow. Most people need 100mg to 200mg of elemental iron daily over several months to accomplish this.

Iron supplements can cause stomach pain, constipation, nausea, vomiting, even diarrhea. Iron turns your stools dark and can causes a metallic taste.

The 3 most common iron supplements are ferrous sulfate, ferrous gluconate, and ferrous fumarate. Ferrous fumarate contains 33% elemental iron, ferrous sulfate has 20% elemental iron, and ferrous gluconate has only 12% elemental iron.

Iron is poorly absorbed and needs an acidic environment for best absorption. Vitamin C (ascorbic acid) improves iron absorption by converting some of it from a less soluble ferric form to a more soluble ferrous form. Vitamin C can increase the amount of iron absorbed from an iron supplement by 10% and from food sources by a factor of four.

Enteric-coated and sustained-release forms of iron are not as well absorbed as rapid-release forms because they dissolve in your intestine instead of your stomach. Your intestines are much less acidic than your stomach, causing less iron to be converted to its more absorbable ferrous form.

Taking iron supplements on an empty stomach, either 30 minutes before or 2-3 hours after eating also improves iron absorption.

Mabel's follow-up blood test showed she was still low in iron. She was taking one capsule daily, but as ferrous gluconate 300mg sustained-release instead of ferrous sulfate 300mg tablets. 300mg ferrous gluconate capsules contain only 36mg of elemental iron, compared to 65mg elemental iron in 300mg ferrous sulfate tablets. We increased the dose to 2 pills daily to make up the difference.

Here are 7 Tips for Taking Iron Supplements Successfully:

1.Check the amount of elemental iron.

Ferrous gluconate 300mg has 36mg of elemental iron, compared with 65mg in ferrous sulfate. 300mg or 325mg tablets are interchangeable.

2.Try taking them on an empty stomach.

If taking your iron supplement on an empty stomach causes stomach irritation, take it with food instead of skipping doses.

3.Avoid sustained-release or enteric-coated iron supplements.

Although they may cause less intestinal irritation, you'll get less iron from sustained-release, delayed-release, and enteric-coated iron supplements. 

4.Take one tablet daily to start.

Take your iron supplement more frequently if instructed to by your doctor. Higher doses of iron are not absorbed as well.

5.Consider using cast iron skillets and pans.

Cooking with cast iron increases the iron content of your food and can treat mild iron deficiency.

6.Add vitamin C to your diet.

One small glass of orange juice or vitamin C tablet improves iron absorption.

7.Keep iron tablets out of the reach of children.

Brightly colored, shiny ferrous gluconate and ferrous sulfate tablets look just like chocolate M&M candies.

Dr. Louise Achey, Doctor of Pharmacy, is a 42-year veteran of pharmacology and author of Why Dogs Can’t Eat Chocolate: How Medicines Work and How YOU Can Take Them Safely. Get clear answers to your medication questions at her website and blog® 2021 Louise Achey



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