mineral
Iron: Elemental Iron, Timing, Vitamin C and Tea
Also known as iron supplement, ferrous sulfate, ferrous gluconate, ferrous fumarate, ferric citrate, iron bisglycinate, iron tablets
Short answer
Iron is a mineral the body uses to make hemoglobin, which carries oxygen in red blood cells. Labels list elemental iron, not the compound weight. Vitamin C helps absorb plant iron, while calcium, tea and coffee can reduce absorption. The adult upper limit is 45 mg a day. Keep iron away from children: overdose can be fatal [1][2].
Last reviewed · 4 sources
What is Iron?
Iron is a mineral the body uses to make hemoglobin, the protein in red blood cells that carries oxygen from the lungs to the tissues [1]. It is also part of myoglobin, which supplies oxygen to muscles, and is needed for growth, brain development, cell function and making some hormones [1]. Food has two types: heme iron from meat, seafood and poultry, and nonheme iron from plants and fortified foods [1]. Heme iron is absorbed better [1].
Forms of Iron you'll see on labels
Ferrous sulfate
A common iron salt; about 20% elemental iron by weight [1].
Ferrous gluconate
About 12% elemental iron by weight [1].
Ferrous fumarate
About 33% elemental iron by weight [1].
Ferric citrate and ferric sulfate
Ferric salts. Ferrous iron dissolves better, so it is more bioavailable than ferric iron [1].
Iron amino acid chelates, carbonyl iron, heme iron polypeptides, polysaccharide-iron complexes
These might cause fewer stomach side effects than ferrous or ferric salts [1].
How much Iron do adults need?
NIH lists these Recommended Dietary Allowances (RDA) for adults, in mg. People on vegetarian diets need 1.8 times more because plant iron is absorbed less. Reference values, not a personal recommendation.
| Group | Amount per day |
|---|---|
| Men 19+ | 8 mg |
| Women 19–50 | 18 mg |
| Women 51+ | 8 mg |
| Pregnancy 19–50 | 27 mg |
| Lactation 19–50 | 9 mg |
Upper limit: 45 mg a day for adults 19+, including during pregnancy and lactation, from food and supplements. Doctors sometimes prescribe more to treat iron deficiency anemia [1].
How Iron appears on a label
The Supplement Facts panel lists elemental iron, which is the actual iron, so you do not need to work it out from the compound (for example, ferrous sulfate is only about 20% iron) [1]. Amounts are in mg. The Daily Value (DV) is 18 mg for adults and children 4 and older; many iron-only products give 65 mg (360% DV) [1]. Solid iron products must carry an FDA warning that accidental overdose is a leading cause of fatal poisoning in children under 6 [1].
When to take Iron
NHS advice for ferrous sulfate is that it works best on an empty stomach, 30 minutes before or 2 hours after eating, but it can be taken with or after food if it upsets your stomach [2]. NIH notes that taking iron with food can help reduce stomach side effects [1]. NIH says experts suggest taking calcium and iron supplements at different times of day [1].
What to keep apart from Iron
Vitamin C (or orange juice)
Vitamin C helps the body absorb nonheme (plant) iron [1]. A doctor or pharmacist may suggest taking iron with orange juice or vitamin C [2].
Calcium (supplements, milk and dairy)
Calcium might reduce absorption of both heme and nonheme iron, though this is not definitively established [1]. Experts suggest taking calcium and iron supplements at different times of day [1].
Tea and coffee
NHS advice is not to take iron tablets with tea, coffee, eggs or dairy, and to leave a 2-hour gap [2]. Polyphenols in some plant foods also reduce nonheme iron absorption [1].
Zinc
Iron supplements of 25 mg or more can reduce zinc absorption [1].
Levothyroxine
Iron can reduce levothyroxine absorption. Some labels advise not taking levothyroxine within 4 hours of iron [1]. Ask your pharmacist.
Levodopa
Iron supplements may reduce levodopa absorption [1]. Ask your pharmacist.
Proton pump inhibitors (PPIs)
PPIs lower stomach acid and can reduce nonheme iron absorption [1]. Ask your pharmacist.
Antibiotics, antacids and other medicines
The NHS lists antacids, some antibiotics (such as doxycycline and ciprofloxacin), bisphosphonates and some HIV medicines as interacting with iron, and advises leaving a gap [4]. Ask your pharmacist how long.
Foods that contain Iron
- Fortified breakfast cereals
- Oysters
- White beans, kidney beans and chickpeas
- Beef liver
- Lentils
- Spinach
- Tofu
- Dark chocolate
- Sardines
- Beef
- Dried fruit such as apricots and raisins
Who should ask a doctor or pharmacist first
Talk to a doctor before taking iron if you have hemochromatosis, a genetic condition that causes iron to build up; treatment guidelines advise avoiding iron and vitamin C supplements [1]. Ask a pharmacist first if you take levothyroxine, levodopa, PPIs, antacids, antibiotics or bisphosphonates [1][4]. If you think you are low in iron, see a doctor for a blood test before taking iron [3].
Keep Iron in a routine that fits
Supin schedules what you take by time of day, reminds you, and tells you when a bottle runs low.
Iron: questions people ask
Elemental iron is the amount of actual iron in a supplement. Supplement Facts labels list it, so you do not need to calculate it from the compound weight [1].
NHS advice for ferrous sulfate is to take it on an empty stomach, 30 minutes before or 2 hours after eating, or with food if it upsets your stomach [2]. Follow your doctor's instructions if iron was prescribed.
NHS advice is not to take iron tablets with tea or coffee, and to leave a 2-hour gap [2].
Calcium might interfere with iron absorption, so experts suggest taking calcium and iron supplements at different times of day [1].
NIH says iron amino acid chelates, carbonyl iron, heme iron polypeptides and polysaccharide-iron complexes might cause fewer stomach side effects than ferrous or ferric salts [1].
Sources
- Iron: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements
- How and when to take ferrous sulfate — NHS
- Iron deficiency anaemia — NHS
- Taking ferrous sulfate with other medicines and herbal supplements — NHS
Educational information, not medical advice. The amounts above are official reference values, not a recommendation for you. Check with your doctor or pharmacist before starting or changing supplements, especially if you take medication, are pregnant or have a health condition. Supin sells a subscription, not supplements. Last reviewed .