Can I take iron and calcium together?
Not at the same time, according to NIH. Calcium might interfere with iron absorption, although this effect has not been definitively established, so experts suggest taking individual calcium and iron supplements at different times of the day [1]. NHS advice for ferrous sulfate tablets also says calcium can reduce their effect [2].
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What the sources say about iron and calcium
NIH says calcium might interfere with the absorption of iron, although this effect has not been definitively established [1]. Unlike other inhibitors of iron absorption, calcium might reduce the absorption of both heme iron (richest in lean meat and seafood) and nonheme iron (found in nuts, beans and vegetables) [1]. NIH adds that a typical western diet blunts the effects of absorption enhancers and inhibitors, so they have little effect on most people's iron status [1]. The NHS lists supplements containing calcium among those to tell a pharmacist or doctor about before starting ferrous sulfate, and says calcium can reduce its effect [2].
How to time them
No official source gives a set number of hours between calcium and iron supplements; NIH says only that experts suggest taking them at different times of the day [1]. For prescribed iron, the NHS advises leaving a gap between ferrous sulfate and other medicines and asking a doctor or pharmacist how long it should be [2]. NHS advice is that ferrous sulfate 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 [3]. The NHS also says not to take it with dairy products, tea, coffee or eggs, and to leave a 2-hour gap before having them [3]. For calcium, NIH says supplements are generally absorbed better with food, calcium citrate can be taken without food, and absorption is highest at doses of 500 mg or less [4].
Who should ask a doctor or pharmacist first
Tell a doctor before taking iron tablets if you have haemochromatosis or haemosiderosis, a type of anaemia not caused by low iron, sickle cell anaemia or thalassaemia, or a stomach or bowel problem [5]. Ask a pharmacist first if you take levothyroxine, dolutegravir or a quinolone antibiotic such as ciprofloxacin, since iron and calcium can both interact with these [2][4]. The NHS also lists levodopa, antacids, bisphosphonates and tetracycline-type antibiotics such as doxycycline for iron [2], and NIH lists lithium for calcium [4]. If you are pregnant, NIH cites the Dietary Guidelines for Americans: take an iron supplement when an obstetrician or other health care provider recommends it [1].
Supin schedules what you take around each other
Supin builds your routine by time of day and keeps iron out of the slot with calcium, magnesium or zinc.
Questions people ask next
No source says which to take first. NIH only suggests taking calcium and iron supplements at different times of the day [1].
NIH says calcium might reduce the absorption of both heme and nonheme iron, but that a typical western diet blunts the effects of enhancers and inhibitors, so they have little effect on most people's iron status [1].
Sources
- Iron: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements
- Taking ferrous sulfate with other medicines and herbal supplements — NHS
- How and when to take ferrous sulfate — NHS
- Calcium: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements
- Who can and cannot take ferrous sulfate — NHS
Educational information, not medical advice, and not a recommendation for you. Check with your doctor or pharmacist before starting, combining or changing supplements, especially if you take medication, are pregnant or have a health condition. Supin sells a subscription, not supplements. Last reviewed .