Iron Supplements: Best Time to Take, Heme vs Non-Heme

What is iron?

Iron is a mineral your body needs to make blood. It's the key ingredient in hemoglobin, the protein in red blood cells that grabs oxygen and carries it throughout your body.

In simple terms, iron is a part of the 'oxygen delivery truck.' Without enough iron, there are fewer trucks, so less oxygen reaches your brain, muscles, hands, and feet. That's why you feel tired, dizzy, and cold in your hands and feet. Iron is also used to make thyroid hormone and dopamine (a brain chemical involved in motivation).

Women lose iron every month through their periods. It's so common that data shows 1 in 4 women worldwide, and over 40% of pregnant women at most, are low in iron.

Iron deficiency symptoms checklist

The more of these that apply, the more it's worth looking at iron.

□ You wake up tired, and even vitamins don't give you energy
□ You get dizzy when you stand up, and have repeat headaches that pain relievers don't help much
□ Your hands and feet are always cold
□ Your face looks pale or dull, with dark under-eye circles
□ The inside of your lower eyelid, your tongue, or your nail beds look pale
□ Your hair is thinning and falling out all over
□ You can't focus and feel foggy
□ You have bad period cramps or heavy periods

You can be low in iron even if your blood test says 'no anemia.' Often hemoglobin is normal but your stored iron (ferritin) is nearly empty. If you get tested, ask for your ferritin level too.

Not all dizziness comes from low iron, though. If it lasts, see a doctor to find the cause first.

Iron supplement benefits: who may benefit

Women in their 30s and 40s, and women with heavy periods: The group most likely to run low on iron.
People who rarely eat meat, are thin, or are dieting: To get 15 mg of iron from food, you'd need to eat nearly 1.3 pounds (600 g) of beef every day.
Hair loss in women: Data suggests 30–70% of female hair loss is linked to low iron. One study found more than half improved after iron levels were restored.
During pregnancy and after birth: Your needs rise sharply because you're sharing blood with your baby. It's common to start around week 16 of pregnancy and continue for about 3 months after giving birth.
Restless legs (an itchy, crawly feeling in the legs at night), an underactive thyroid, and older adults who make less stomach acid and eat less meat should also check whether they're low in iron.

Who can skip it, or should ask first

Healthy men under 40: Most don't need to take it separately. Even in middle age and beyond, consider it only if you have symptoms.
People already taking a multivitamin with iron: That's usually enough.
People whose lab numbers are back to normal: You can stop at that point.
People in cancer treatment (chemo or radiation): Studies suggest cancer cells also use iron. Even if you have anemia, always talk to your doctor before taking it.
People with gut conditions like ulcers or colitis: High doses can rarely cause problems, so check with your doctor.
Babies and children: Preterm babies, and children who eat little solid food or are breastfed only for a long time, may need iron. Talk to your pediatrician.

Types of iron: heme vs non-heme vs chelate

The biggest complaints with iron supplements are constipation and heartburn. The form affects absorption, how easy it is on your stomach, cost, and how much iron is in each pill.

Type	What to know	Best for
Heme iron (the same form as iron in meat)	Absorbs well with less constipation and heartburn. Pricey, with a low amount per pill.	People worried about constipation, pregnant women, people who couldn't tolerate iron before
Standard iron (non-heme, like ferrous sulfate or ferrous fumarate)	Inexpensive and often high-dose. Low absorption, so constipation and heartburn are common.	People without constipation, people with anemia who need a large dose
Chelate (bisglycinate)	Wrapped in amino acids to boost absorption and go easier on the stomach. Good value.	First-timers and anyone who wants a safe all-around pick
Coated iron (liposomal, egg protein, microencapsulated)	The iron is wrapped in a coating, and many people say it causes less constipation. Research is still limited.	People who got constipated on standard iron

If you have constipation, start with heme or coated iron. If you need a large dose, start with standard iron or a chelate. The right iron differs from person to person, so if one doesn't agree with you, try a different form.

Daily iron dose and how long to take it

Bottom line: If you only have symptoms, take 12–20 mg a day and don't go over 40 mg. If you've been diagnosed with anemia, follow the higher dose your doctor prescribes.

Situation	Daily dose (elemental iron)
No anemia, but fatigue, dizziness, or cold hands and feet	12–20 mg
Severe period cramps	20 mg or more
Pregnancy	25–30 mg on average
Upper limit for supplements	About 40 mg
Diagnosed anemia	Higher dose prescribed by your doctor (tens of mg to 100+ mg)

Here's how to think about how long to take it.

Your levels rise in 1–2 months, but if you stop then, they tend to drop again.
Keep going for at least 4 months. With anemia, it can take up to 12 months.
Once your levels are normal, you can stop.
If you took a high dose over 40 mg for a long time, take a break of about the same length.

Taking tens of mg to 100 mg a day when you don't have anemia is too much. At a proper dose, your gut adjusts how much it absorbs on its own, so there's little risk of iron building up.

Best time to take iron: empty stomach or after meals?

Iron absorbs best on an empty stomach. Before breakfast or at bedtime works well.

If it causes heartburn or nausea, move it to right after a meal. Absorption drops a little, but taking it consistently matters more.

Every-other-day dosing is another option. You take two days' worth at once, then skip the next day. Some data shows better absorption and less constipation this way.

Things that block absorption when taken together

Coffee, green tea, black tea: Tannins (the compounds that make them taste astringent) bind to iron and can cut absorption by up to 80%. Take it with water.
Calcium: Clearly blocks absorption at 800 mg or more at one time. Space them apart if you can.
Zinc and magnesium: Minerals compete with each other for absorption. Take them at different times. Heme iron uses a different absorption pathway, so it's less affected.
Some antibiotics (quinolones, tetracyclines): They block each other's absorption. Space them 2–4 hours apart.

Should you take it with vitamin C? It's known to help absorption, but in 2021 the British Society of Gastroenterology dropped this recommendation. With today's chelated and coated irons, you don't need to take them together.

How to choose an iron supplement: 3 things to check on the label

The form — Look inside the parentheses, as in 'Iron (as ferrous bisglycinate).' If constipation is a worry, choose heme iron or a coated form.
How many mg of elemental iron per pill — For symptoms, around 12–20 mg is a safe range. Many US products have 18 mg per pill.
Whether your multivitamin already has iron — If it does, keep the total under 40 mg. If you take a multivitamin, a basic iron supplement is enough.

If your levels are borderline, try it for 1–2 weeks first, and keep going if you feel better.

Iron side effects: constipation, black stools, stomach upset

The most common side effects are constipation, heartburn, and indigestion, especially with standard iron.

If it bothers you, try these steps in order.

Move it to right after a meal
Switch to every-other-day dosing
Change to heme or coated iron
Lower the dose

Black stools are caused by iron that wasn't absorbed, so they're nothing to worry about. Liquid iron can stain your teeth.

What about your liver? At supplement levels (40 mg or less), there's no need to worry. Liver problems happen at dozens of times the normal amount, like thousands of mg a day.

Keep iron out of children's reach. Most iron accidents happen when a child swallows several pills. More than 20 mg per kg of body weight can cause gut damage and shock.

Medications and conditions to watch

Caution During chemo or radiation — Cancer cells may also use iron — even with anemia, always talk to your doctor
Check Quinolone and tetracycline antibiotics — They block each other's absorption — space them 2–4 hours apart
Note Coffee, green tea, black tea — Tannins bind to iron and sharply reduce absorption — take with water and keep them apart
Note Calcium — Blocks absorption at 800 mg or more at one time — space them apart if you can
Note Zinc — Minerals compete for absorption — take at different times
Note Magnesium — Minerals compete for absorption — take at different times (heme iron is less affected)

Combinations

Works well with: Vitamin C, B vitamins (B complex), Folate (Folic Acid)

Space apart from: Calcium, Zinc, Magnesium, Alpha-Lipoic Acid

How it appears on the label

Match the names on the Supplement Facts panel with the forms of Iron explained on this page.

On the label	What it is	What it means
Ferrous Bisglycinate Iron Bisglycinate Ferrochel	Iron bisglycinate (chelated iron)	Usually easier on the stomach
Ferrous Sulfate	Ferrous sulfate	The most common and lowest cost, but can upset your stomach
Ferrous Fumarate Ferrous Gluconate	Ferrous fumarate / ferrous gluconate	Standard forms of iron
Heme Iron Polypeptide	Heme iron	The same form of iron found in meat
Carbonyl Iron	Carbonyl iron	Iron that absorbs slowly

Best Iron supplements on Amazon, compared

Bottom line

We checked the labels of 27 popular iron products on Amazon: 5 recommended, 18 depend on your needs, 4 not recommended.

Best overall — NOW Foods Iron 18 mg (Ferrochel) Veg Capsules: Ferrochel (Albion chelate) 18 mg — just right for managing symptoms (Per serving: 18 mg)
Best value — Nature's Bounty Gentle Iron 28 mg Capsules: Gentle bisglycinate 28 mg — right for heavy periods (Per serving: 28 mg)
Higher dose — Doctor's Best High Absorption Iron with Ferrochel 27 mg: Well-absorbed Ferrochel (bisglycinate) 27 mg (Per serving: 27 mg)
Liquid — Nature's Way Liquid Iron 18 mg Berry (16 fl oz): Chelated iron 18 mg per tablespoon (15 mL) — a good amount (Per serving: 18 mg)
Diagnosed anemia — Nature Made Iron 65 mg (325 mg Ferrous Sulfate) Tablets: Ferrous sulfate 65 mg — a high dose used for diagnosed anemia (Per serving: 65 mg)

We checked the labels of popular Amazon products and rated them by the criteria above. Cost per day is relative — compared with other products of the same supplement. Check Amazon for the current price.

Best overallIron 18 mg (Ferrochel) Veg CapsulesNOW Foods Best valueGentle Iron 28 mg CapsulesNature's Bounty Higher doseHigh Absorption Iron with Ferrochel 27 mgDoctor's Best LiquidLiquid Iron 18 mg Berry (16 fl oz)Nature's Way Diagnosed anemiaIron 65 mg (325 mg Ferrous Sulfate) TabletsNature Made

Recommended 5

RecommendedNOW Foods

Iron 18 mg (Ferrochel) Veg Capsules

Bisglycinate chelate (Ferrochel) · Per serving: 18 mg · Cost per day: low

Ferrochel (Albion chelate) 18 mg — just right for managing symptoms
Only basic fillers like rice flour
Low cost per day

First-timers, managing symptoms like fatigue or dizziness

Iron supplements: who should take them, when, and which kind

What is iron?

Iron deficiency symptoms checklist

Iron supplement benefits: who may benefit

Who can skip it, or should ask first

Types of iron: heme vs non-heme vs chelate

Daily iron dose and how long to take it

Best time to take iron: empty stomach or after meals?

How to choose an iron supplement: 3 things to check on the label

Iron side effects: constipation, black stools, stomach upset

Medications and conditions to watch

Combinations

How it appears on the label

Best Iron supplements on Amazon, compared

Bottom line

Recommended 5

Iron 18 mg (Ferrochel) Veg Capsules

Iron 18 mg Capsules

High Absorption Iron with Ferrochel 27 mg

Gentle Iron 25 mg Vegetable Capsules

Gentle Iron 28 mg Capsules

Depends on your needs 18

Iron Bisglycinate 25 mg Capsules

Double Strength Iron 36 mg (Ferrochel) Veg Capsules

Iron-C Capsules

Advanced Iron Complex (formerly Ferrasorb)

Blood Builder Iron Tablets

Vitamin Code Raw Iron Capsules

Vitamin Code Healthy Blood Capsules

Iron 65 mg (325 mg Ferrous Sulfate) Tablets

Iron 65 mg (325 mg Ferrous Sulfate) Tablets

Iron Supplement Plus Vitamin C Tablets

Slow Release Iron 45 mg Tablets

Liquid Iron 18 mg Berry (16 fl oz)

Vegan Liquid Iron Berry (15.22 fl oz)

Original Iron 65 mg Tablets

Chelated Iron 28 mg Tablets (400 ct)

Complete Iron Caplets with Bifera

Active Iron 25 mg

SiderAL Forte Sucrosomial Iron

Not recommended 4

Slow Release Iron 45 mg Tablets

Hema-Plex Iron Softgels

Hema-Plex Iron Slow-Release Tablets

Iron + Herbs Liquid (8.5 fl oz)

Frequently asked questions

Related concerns