When to take Iron
Also known as Ferrous sulfate, Ferrous gluconate, Ferrous fumarate, Iron bisglycinate
Iron is best absorbed on an empty stomach, but you can take it with a small amount of food if it upsets your stomach. Do not take it at the same time as coffee or other caffeine drinks, and wait at least 2 hours after milk, calcium or antacids before taking iron.
Last reviewed October 13, 2026
Timing
| Best time | Any time of day |
|---|---|
| Food | On an empty stomach |
| Fat-soluble | No |
- Any time; consistency matters more than timing.
- Iron is best absorbed on an empty stomach. If it causes cramps or nausea, a small amount of food can help.
- Taking vitamin C or a glass of orange juice with your iron pill can help your body absorb it.
- Do not take iron at the same time as coffee, caffeinated tea or other drinks with caffeine, or with high-fiber foods like bran, whole grains and raw vegetables.
- Iron supplements of 25 mg or more can lower how much zinc you absorb.
Keep apart
Check with your doctor first if…
- Keep away from children: accidental iron overdose is a leading cause of fatal poisoning in children under 6. If a child swallows iron, call a doctor or poison control right away.
- Upper limit: 45 mg a day for adults unless your doctor prescribes more. Doses of 45 mg a day or more often cause constipation, nausea or stomach upset.
- Black stools are normal on iron. Call your doctor if stools look tarry or have red streaks, or if you get cramps or sharp stomach pain.
- Thyroid medicine (levothyroxine): do not take it within 4 hours of iron.
- Other medicines: iron can make levodopa and some antibiotics (tetracycline, penicillin, ciprofloxacin) work less well. Acid reducers lower iron absorption, so wait at least 2 hours between them and iron.
- Hemochromatosis (iron overload): do not take iron supplements unless your doctor tells you to.
- Ask your provider how much iron to take; taking more than your body needs can cause serious problems.
Amounts studied
RDA: 8 mg a day for men and for women 51+, 18 mg a day for women 19–50, 27 mg a day in pregnancy. UL: 45 mg a day for adults. Pregnancy trials used 9–90 mg a day; a blood donor trial used 37.5 mg a day. The label lists elemental iron.
Follow the serving size on your product’s label.
What the research says
| Area | Evidence | Summary |
|---|---|---|
| Healthy iron levels in pregnancy | Strong | A Cochrane review found daily iron (9–90 mg) cut the chance of low iron at the end of pregnancy by 57%. U.S. guidelines say pregnant women should take iron when their provider recommends it.[1] |
| Iron levels after blood donation | Limited | In one trial of 215 blood donors, 37.5 mg a day of iron helped them recover lost iron and hemoglobin in less than half the time.[1] |
Questions
Can I take iron with coffee or tea?
Not at the same time. MedlinePlus advises against foods or drinks with caffeine when you take your iron. Have your coffee or caffeinated tea at a different time.
Can I take iron and calcium together?
It is better not to. Calcium may reduce iron absorption, so experts suggest taking them at different times of day. MedlinePlus says to wait at least 2 hours after calcium or milk before taking iron.
Should I take iron on an empty stomach?
Yes, if you can. Iron is best absorbed on an empty stomach, but if it causes cramps or nausea, take it with a small amount of food. Vitamin C or orange juice can help absorption.
Can I take iron with zinc?
Iron supplements of 25 mg or more can lower zinc absorption and blood zinc levels. The NIH fact sheet does not give a set gap in hours, so ask your doctor or pharmacist if you take both.
How long does iron take to work?
For people with low iron, MedlinePlus says blood counts usually return to normal after about 2 months. Iron is often continued for another 6 to 12 months to rebuild the body's stores.
Plan your whole routine
Add Iron and everything else you take to the planner to see your morning, midday and evening, and what to keep apart.
Open the plannerSources
- Iron: Fact Sheet for Health Professionals, NIH ODS (accessed October 13, 2026)
- Taking iron supplements, MedlinePlus (accessed October 13, 2026)
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. It is general information, not medical advice: talk with your doctor or pharmacist before starting a supplement, especially if you are pregnant, breastfeeding, take medicine or have a health condition.