Jun 4, 2025
Maximizing Iron Supplement Absorption: How to Take Iron Pills Correctly and Get Real Results
Learn the best time to take iron supplements, what helps and hurts absorption, and how to avoid common mistakes.
Blood Vessels and Heart
Written by
Mito Team
Why Iron Matters and Why It’s Hard to Absorb
Iron plays a critical role in your body. It helps carry oxygen in your blood, supports muscle function, and powers your immune system. But despite its importance, many people—especially women—don’t get enough.
Iron deficiency anemia (IDA) is one of the most common nutrient deficiencies worldwide. While oral iron supplements are the go-to treatment, they don’t always work as expected. Why? Because iron absorption is tricky. Timing, diet, inflammation, and even the type of iron supplement all play a role in how well your body uses it.
In this guide, we’ll show you how to take iron pills correctly, when to take them for best results, and what helps absorb iron, so you can feel better, faster.
Understanding How Iron Is Absorbed
Iron is absorbed mostly in the upper part of your small intestine (the duodenum), where it enters your bloodstream through specialized transporter proteins. But your body tightly regulates this process through a hormone called hepcidin. When hepcidin levels are high, like during inflammation or after a dose of iron, your body blocks further absorption.
That’s why more iron isn’t always better, and why taking iron at the wrong time can lead to poor results.
How to Take Iron Supplements for Best Absorption
Best Time to Take Iron Supplements
On an empty stomach: Iron absorbs best when your stomach is empty. Aim to take it at least 1 hour before or two hours after a meal.
Taking iron at night can work well, but make sure you haven’t eaten for a couple of hours. Avoid right after exercise. Intense workouts raise hepcidin and may reduce iron absorption.
If iron upsets your stomach, it’s okay to take it with a small snack. Just know that absorption may drop by up to 66%.
Alternate-Day Dosing Is Smarter
Newer research shows that taking iron every other day, rather than daily, can double absorption. Why? Because it gives hepcidin time to return to baseline, allowing your next dose to absorb better.
Pro tip: Ask your doctor if alternate-day dosing could work for you.
How Much Iron Can You Absorb in a Day?
Even if you take a 100 mg iron pill, your body might only absorb 10 to 20 mg. Higher doses aren’t always better. They can cause more side effects and raise hepcidin. That’s why smaller, smarter doses often work better than large daily ones.
What Helps Absorb Iron and What Blocks It
Iron Absorption Enhancers
Vitamin C: Take your iron with orange juice or a Vitamin C supplement. It can significantly boost absorption.
Heme iron foods: Meat, fish, and poultry not only provide easily absorbed iron, but they also help you absorb more non-heme iron from plants or supplements.
Iron Absorption Inhibitors
To avoid reducing iron absorption, skip the following within two hours of your supplement:
Inhibitor | Examples | What to Do |
Calcium | Milk, dairy, and antacids | Separate by more than 2 hours |
Phytates | Grains, legumes, and seeds | Take iron between meals |
Polyphenols | Tea, coffee, cocoa | Drink separately and avoid with meals |
Other minerals | Zinc, magnesium | Avoid combining in one supplement |
Medications | PPIs, thyroid meds | Talk to your doctor about timing |
Choosing the Right Iron Supplement
Not all iron supplements are created equal. They differ in how much elemental iron they contain, how well they’re absorbed, and how likely they are to cause side effects. Here’s a quick guide to the most common forms:
Ferrous sulfate: It is one of the most widely used and affordable options. A typical tablet contains 65 mg of elemental iron. It’s effective, but it often causes gastrointestinal issues like nausea or constipation.
Ferrous fumarate: It offers a higher dose, about 108 mg of elemental iron per tablet. While it's strong, it may be tougher to tolerate for some people, especially those with sensitive stomachs or inflammatory bowel issues.
Ferrous gluconate: This contains less elemental iron, about 35 mg per tablet, but is gentler on the stomach. It’s a good option for those who can’t tolerate higher doses.
Iron bisglycinate: This is a newer form of iron that’s bonded with the amino acid glycine. It may be absorbed more efficiently and cause fewer digestive side effects. While often more expensive, it’s a great choice for people who have struggled with other forms.
If side effects are a concern, switching to a different form, or even lowering the dose and taking it on alternate days, can improve both absorption and adherence. At Mito Health, we help you choose the supplement that fits your needs, preferences, and medical history.
What If Oral Iron Supplements Isn’t Enough?
Some people can’t absorb iron well through the gut. You may need intravenous (IV) iron if you have:
Inflammatory bowel disease (IBD)
Chronic inflammation (like lupus or rheumatoid arthritis)
Had bariatric surgery
Severe iron deficiency that doesn’t improve with pills
At Mito Health, we can help determine whether oral or IV iron is best, using your lab results, medical history, and symptoms.
Common Side Effects and How to Manage Them
Taking iron supplements isn’t always easy. Here’s how to handle common issues:
Constipation: Try stool softeners, stay hydrated, and eat more fiber.
Nausea: Take with a small snack, or split the dose into two smaller servings.
Dark stools: Normal and harmless (but tarry, red-streaked stools need medical attention).
Tooth staining (from liquid iron): Use a straw and rinse your mouth afterward.
Still struggling? Switch forms, reduce frequency, or alternate-day dosing often helps.
Can You Take Too Much Iron?
Iron is essential, but too much can be dangerous, especially for kids. Symptoms of iron overdose include vomiting, confusion, and, in severe cases, coma. Never supplement without a diagnosis, and keep iron out of reach of children.
Why Testing Your Iron Levels Matters
Before starting an iron supplement, it’s important to get your blood tested. At Mito Health, we check your iron status, including ferritin levels, serum iron, transferrin saturation, and total iron-binding capacity (TIBC).
This full picture helps determine whether you’re low in iron, how much you need, and how long to supplement. We also help monitor your progress, so you’re not flying blind.
Take Iron Pills Correctly and Feel Better
Taking iron pills correctly comes down to timing, pairing, and consistency. For best absorption, take your supplement on an empty stomach or before bed, and pair it with vitamin C while avoiding common blockers like calcium or coffee. Even though pills may contain high doses, your body only absorbs about 10 to 20 mg a day, so more isn’t always better.
At Mito Health, we help you get it right with personalized testing and expert guidance every step of the way. Get started here.