The 5 Best Iron Supplements That Won't Upset Your Stomach

An iron deficiency can leave you feeling tired, cold and weak, according to the Mayo Clinic. Taking daily iron pills can bring your levels up and help you feel better — but, it may also upset your stomach.

"Gentle" iron supplements are formulated to reduce gastrointestinal side effects — for instance, there are some iron supplements that are less likely to cause constipation or diarrhea. Plus, you can lessen your symptoms by taking your supplement with certain foods.

Here are some of the best iron supplements to try if iron upsets your stomach.

Iron in supplements comes in many different forms, including ferrous, ferric (iron salts), carbonyl iron, heme iron polypeptides, iron amino-acid chelates and polysaccharide-iron complex, says dietitian Cristina Caro, RDN and spokesperson for the hospitality group Sodexo.

They're all easily absorbed when taken with water, per ConsumerLab, an organization that tests health products. But taking them without food can sometimes lead to GI issues.

If you often experience side effects from iron supplements, ConsumerLab suggests trying these types of iron, which are still well-absorbed:

• ferrous bisglycinate
• ferrous glycinate
• iron amino acid chelates

Gentle iron supplements are not without side effects, but you may find that they reduce stomach upset to a more tolerable level.

The FDA doesn't regulate supplement safety and efficacy. So to find the best gentle iron supplements on the market, we spoke to a dietitian for her top picks and chose products that have verification from independent quality control organizations such as:

• NSF
• Consumer Lab
• United States Pharmacopeial Convention (USP)

This supplement has iron amino acid chelates (ferrous bisglycinate). "It can be taken with food to reduce irritation while still being absorbed well," Caro says.

Nature's Bounty Gentle Iron is also a top pick from ConsumerLab. These iron pills are both vegetarian and kosher.

ConsumerLab deems this GNC pick the top low-cost iron protein chelate supplement — and because it's made of iron protein chelate, you know it won't upset your stomach.

It's both wheat- and gluten-free.

Vegans and vegetarians miss out on heme iron, a form of the mineral that's found in red meat and is easily absorbed, per the Mayo Clinic. NOW's vegan iron supplement uses a form of iron that can be taken with food but still absorbs well, Caro says.

NOW Iron is also a top pick from ConsumerLab. With 18 milligrams of iron, it provides 100 percent of your daily value (DV). That's the precise amount recommended for people assigned female at birth between the ages of 19 and 50, according to the National Institutes of Health (NIH).

Children, people assigned male at birth and people post-menopause require far less of this mineral.

If you struggle with GI issues when you take iron supplements, an extended-release option — such as Slow Fe Slow Release Iron — may be beneficial. This type of supplement will deliver iron over a longer period, Caro says.

While it may mean you absorb less iron, the supplement will have less of an effect on your appetite and up the chances that you'll stick with taking it, Caro says.

This supplement offers 250 percent of your DV of iron.

As you've seen, many iron supplements offer a lot of iron — far more than your DV. If you're looking to add iron, but don't want to overdo it, Fergon High Potency is a good option, with 150 percent of your DV of iron.

This supplement won't cause stomach-related side effects, according to the manufacturer.

Iron is best absorbed when taken on an empty stomach, according to the U.S. National Library of Medicine (NLM). Still, taking iron pills with a small amount of food may help prevent your upset stomach.

But choose what you eat carefully: "Foods and beverages containing caffeine, calcium, fiber, phytates or tannins can interfere with iron absorption," Caro says.

Make sure to wait until 2 hours after you've taken an iron supplement to eat these foods:

• Caffeinated foods: Coffee, tea, some sodas, energy drinks, chocolate
• Calcium-rich foods: Milk, cheese, yogurt
• Fiber-rich foods: Whole grains, raw vegetables, bran
• Foods with tannins: Coffee, tea, wine, chocolate

Instead, choose foods high in vitamin C — fruits and vegetables — which improve iron absorption, Caro says.

Increasing your intake of iron-rich foods may help resolve your iron deficiency sooner so you can stop taking iron pills. Eating these foods regularly can prevent iron deficiency in the future.

Some of the best food sources of iron, according to the NIH, include:

• Meat
• Seafood
• Poultry
• Iron-fortified cereals and breads
• White and kidney beans
• Lentils
• Peas
• Nuts

As with supplements, you should avoid eating dairy foods, caffeine and spinach with iron-rich foods. Pairing these foods with a source of vitamin C can help improve absorption.