Which iron supplement is best?
There is no “best” type of iron supplement. Inexpensive supplements are widely available and generally work just as well as more expensive iron formulations.
The human body usually does a pretty good job of keeping iron in balance. Despite this, iron deficiency is common, especially in people who menstruate. It’s also common for people to have low iron and not know it. But this doesn’t mean everyone should take extra iron.
✅ Check out this previous TNG post, “Should I take an iron supplement?”.
Getting enough dietary iron is a good way to ensure your iron stores are adequate. Red meat, dark poultry meat, and shellfish are some of the best food sources. Plenty of plant-based foods are rich in iron too. Nut, beans, fortified grains, and dried fruits are a few iron-rich examples. However, iron from vegetarian sources is less absorbed — meaning less iron moves from your gut into your body.
If you have nutritional gaps, a small amount of extra iron, such as in a multivitamin, might help. However, extra iron from foods or a multivitamin isn’t usually enough if your iron stores are low. Instead, a separate iron supplement is used to treat iron deficiency. Taking an iron supplement is especially important if you have iron deficiency anemia.
➡️ Choosing an oral iron supplement
Oral iron supplements come in many different chemical forms and combinations. Although marketing claims may tout the unique benefits of a particular (usually more expensive) iron supplement, there isn’t enough evidence to say one type is more effective or better tolerated.
Starting with an iron supplement that’s cheapest and easiest for you to get is usually the best way to go. Iron pills are sold over the counter. Your clinician still might order them for you through your pharmacy to get them covered by your insurance.
Ferrous iron salts are the most popular iron formulations. Common ones include:
✅ Ferrous sulfate
✅ Ferrous gluconate
✅ Ferrous fumarate
Other iron formulations might have certain advantages. However, these iron formulations often cost more, and they haven’t been proven to work better than ferrous iron salts. Still, they’re suitable options if you don’t mind paying extra for a difference that may not matter.
✅ Iron protein succinylate: may be gentler on your stomach (contains milk protein)
✅ Polysaccharide-iron complexes: may have less metallic taste and stomach upset
✅ Iron amino-acid chelates (ferrous bisglycinate): has fewer dietary interactions
✅ Carbonyl iron: no notable difference from ferrous iron salts
✅ Heme iron polypeptides: may be better absorbed but not suitable for vegetarians
As with any supplement, consider choosing a brand that follows Good Manufacturing Practices (GMP) and uses third-party testing, like U.S. Pharmacopeia (USP). This helps ensure that what’s on the label is actually in the bottle.
💡 A reputable brand isn’t necessarily more expensive.
➡️ Interactions and side effects to know about
Share your medication list with your clinician so they can check for interactions. As a rule, it’s best to space your iron dose apart from other oral medications or supplements. Iron binds to many substances in the gut and blocks their absorption. Additionally, some medications can prevent iron from being absorbed. Your clinician can give you specific information about the timing since it varies depending on the medication or supplement.
Common oral iron side effects include:
✅ Stomach upset (nausea or heartburn)
✅ Constipation
✅ Diarrhea (less common than constipation)
✅ Darker colored stool (not from bleeding)
✅ Temporary teeth staining (liquid formulations)
💡 Enteric-coated (“slow-release”) iron formulations may be easier on your stomach, but they don’t work as well because they’re less well-absorbed.
Fluids, fiber, and physical movement — all the healthy bowel habits that normally keep you regular can help you stay regular while taking iron. Try the following if you start feeling constipated after starting iron:
- Eat more whole fruits and veggies
- Add fiber-rich beans, grains, nuts, and seeds
- Drink extra water between meals
- Take more movement breaks during the day
Iron is best absorbed on an empty stomach. But if it bothers your stomach, try taking your dose with a bit of food. If that doesn’t help, or you experience other bothersome side effects, let your clinician know. They may suggest a lower dose or a different dosing schedule or formulation to help. Intravenous (IV) iron may be another option if you’re still having trouble taking your iron supplement.
➡️ A newer prescription-only oral iron
Accrufer (ferric maltol) is a prescription-only iron supplement that’s approved for iron deficiency in adults. It has a non-salt formulation that may cause fewer gastrointestinal side effects in people who don’t tolerate over-the-counter iron supplements. However, it’s a brand-only medication that’s very expensive and may not be covered by insurance.
Stay nourished. Stay informed. And stay supplement-safe.
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