{"ok":true,"entry":{"slug":"iron","kind":"supplement","name":"iron","aliases":["ferrous sulfate","ferrous fumarate","ferrous gluconate","ferrous bisglycinate","iron chelate"],"brands_sg":["Sangobion","GreenLife","Solgar","NOW Foods"],"class":"mineral","tags":["energy","general","womens-health"],"use_for":"red blood cells, oxygen transport, growth and some hormones","use_after":"with food if it upsets the gut · 4 h away from levothyroxine","use_duration":null,"take_with":"vitamin c or meat lifts uptake · calcium/phytates may cut it","pros":["ferrous forms absorb better than ferric","chelate/polysaccharide forms may be easier on the gut","18 mg in a women's multi covers 100% of the daily value"],"cons":["constipation, nausea, stomach upset at higher doses","25 mg+ taken with zinc blunts zinc uptake","overdose is a top cause of fatal poisoning in under-6s"],"dose_note":"rda 8 mg a day for men and for women 51+, 18 mg for women 19–50, 27 mg in pregnancy; ul 45 mg a day, set on gut side effects; hsa's limit for health supplements is 15 mg a day (30 mg may be considered for pregnancy multis); ods notes many iron-only pills carry 65 mg — above the ul; doctors sometimes prescribe above the ul for diagnosed deficiency","dosage":{"ul":45,"unit":"mg","fda_dv":18,"rda_ai":"8 (men, women 51+) · 18 (women 19–50)","ul_status":"established","population":"general adult","hsa_max_daily":15},"ul_status":"established","sg_class":null,"cautions":["hemochromatosis or iron overload — the sheet says avoid iron and vitamin c supplements; ask your doctor","on levodopa, levothyroxine or a proton pump inhibitor — ask your pharmacist first","children — labels warn: keep out of reach; overdose can be fatal","pregnant — needs rise to 27 mg a day; ask your doctor"],"clashes":[{"src":["nih_ods_iron_hp","nih_ods_iron_con"],"note":"iron cuts its absorption; labels warn it may work less well","with":"levodopa"},{"src":["nih_ods_iron_hp","nih_ods_iron_con"],"note":"iron cuts its absorption; labels advise 4 h apart","with":"levothyroxine"},{"src":["nih_ods_iron_hp","nih_ods_iron_con"],"note":"less stomach acid → less non-heme iron absorbed from food","with":"proton pump inhibitors (omeprazole, lansoprazole)"},{"src":["nih_ods_iron_hp","nih_ods_iron_con"],"note":"may cut iron uptake; experts suggest different times of day","with":"calcium supplements"},{"src":["nih_ods_iron_hp","nih_ods_iron_con"],"note":"iron 25 mg+ taken together cuts zinc absorption","with":"zinc supplements"}],"sources":[{"id":"nih_ods_iron_hp","url":"https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/","label":"NIH ODS — Iron (Health Professional), updated September 4, 2025","quote":"[RDA] 19–50 years: Male 8 mg, Female 18 mg, Pregnancy 27 mg, Lactation 9 mg … 51+ years: Male 8 mg, Female 8 mg … [UL] 19–50 years: 45 mg … 51+ years: 45 mg … Iron is an essential component of hemoglobin, an erythrocyte (red blood cell) protein that transfers oxygen from the lungs to the tissues … Iron is also necessary for physical growth, neurological development, cellular functioning, and the synthesis of some hormones … Heme iron has higher bioavailability than nonheme iron … In addition to ascorbic acid, meat, poultry, and seafood can enhance nonheme iron absorption, whereas phytate (which is present in grains and beans) and certain polyphenols in some nonanimal foods (e.g., cereals, legumes) have the opposite effect … Unlike other inhibitors of iron absorption, calcium might reduce the bioavailability of both nonheme and heme iron … Multivitamin/mineral supplements with iron, especially those designed for women, typically provide 18 mg iron, which is 100% of the Daily Value (DV) … Iron-only supplements usually deliver more than the DV, with many providing 65 mg iron (360% of the DV) … Because of its higher solubility, ferrous iron in dietary supplements is more bioavailable than ferric iron … High doses of supplemental iron (45 mg/day or more) may cause gastrointestinal side effects, such as nausea and constipation … Other forms of supplemental iron, such as heme iron polypeptides, carbonyl iron, iron amino-acid chelates, and polysaccharide-iron complexes, might have fewer gastrointestinal side effects than ferrous or ferric salts … ferrous fumarate is 33% elemental iron by weight, whereas ferrous sulfate is 20% and ferrous gluconate is 12% elemental iron … experts suggest that people take individual calcium and iron supplements at different times of the day … supplements containing 25 mg iron or more can reduce zinc absorption and plasma zinc concentrations … High-dose iron supplements can also cause gastrointestinal effects, including gastric upset, constipation, nausea, abdominal pain, vomiting, and diarrhea … Taking iron supplements with food can help minimize these adverse effects … WARNING: Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6. Keep this product out of reach of children … The American Association for the Study of Liver Diseases recommends that treatment of hemochromatosis include the avoidance of iron and vitamin C supplements … The FNB has established ULs for iron from food and supplements based on the amounts of iron that are associated with gastrointestinal effects following supplemental intakes of iron salts … Physicians sometimes prescribe intakes higher than the UL, such as when people with IDA need higher doses to replenish their iron stores … iron supplements reduce the absorption of levodopa (found in Sinemet and Stalevo), used to treat Parkinson's disease and restless leg syndrome, possibly through chelation … The simultaneous ingestion of iron and levothyroxine can result in clinically significant reductions in levothyroxine efficacy in some patients … advise against administering levothyroxine within 4 hours of iron supplements … Because proton pump inhibitors, such as lansoprazole (Prevacid) and omeprazole (Prilosec), reduce the acidity of stomach contents, they can reduce iron absorption","accessed":"2026-08-27"},{"id":"nih_ods_iron_con","url":"https://ods.od.nih.gov/factsheets/Iron-Consumer/","label":"NIH ODS — Iron (Consumer), updated August 17, 2023","quote":"Your body uses iron to make hemoglobin, a protein in red blood cells that carries oxygen from the lungs to all parts of the body, and myoglobin, a protein that provides oxygen to muscles. Your body also needs iron to make some hormones … Adult men 19–50 years 8 mg … Adult women 19–50 years 18 mg … Adults 51 years and older 8 mg … Pregnant women 27 mg … Vegetarians who do not eat meat, poultry, or seafood need almost twice as much iron as listed in the table … Your body absorbs iron from plant sources better when you eat it with meat, poultry, seafood, and foods that contain vitamin C … In healthy people, taking high doses of iron supplements (especially on an empty stomach) can cause an upset stomach, constipation, nausea, abdominal pain, vomiting, and diarrhea … High doses of iron can also decrease zinc absorption … People with this disorder should avoid using iron supplements and vitamin C supplements … Adults 19+ years 45 mg … A doctor might prescribe more than the upper limit of iron to people who need higher doses for a while to treat iron deficiency … Iron supplements can reduce the amount of levodopa that the body absorbs, making it less effective … Taking iron with levothyroxine can reduce this medication's effectiveness … The proton pump inhibitors lansoprazole (Prevacid) and omeprazole (Prilosec) decrease stomach acid, so they might reduce the amount of nonheme iron that the body absorbs from food … Calcium might interfere with iron absorption. Taking calcium and iron supplements at different times of the day might prevent this problem … Iron in supplements is often in the form of ferrous sulfate, ferrous gluconate, ferric citrate, or ferric sulfate … Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6","accessed":"2026-08-27"},{"id":"fda_dv","url":"https://www.fda.gov/food/nutrition-facts-label/daily-value-nutrition-and-supplement-facts-labels","label":"FDA — Daily Value on the Nutrition and Supplement Facts Labels (Reference Guide: Daily Values for Nutrients), content current as of 03/05/2024","quote":"Iron … 18mg … DVs are the recommended amounts of nutrients to consume or not to exceed each day","accessed":"2026-08-27"},{"id":"hsa_hs_guidelines","url":"https://file.go.gov.sg/hsa-hs-guidelines.pdf","label":"HSA Singapore — Health Supplements Guidelines, GL-CHPB-3-001 Rev. No. 020, January 2026 (clause 4.8 + Table 5 Minerals Limits)","quote":"4.8 HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits stated in Tables 4 and 5 … Table 5: Minerals Limits … Nutrient … Maximum Daily Limit … Iron 15 mg* … *For multivitamin and mineral supplements for pregnant women, a higher iron limit of 30mg/day may be considered … 4.11 Examples of supplements intended for specific adult population groups that require higher levels of supplementation are: … d. Iron for patients with low blood haemoglobin level","accessed":"2026-08-27"},{"id":"watsons_sg_iron","url":"https://www.watsons.com.sg/search?text=iron","label":"Watsons Singapore — site search 'iron' (retail listings, SGD)","quote":"[SANGOBION] Sangobion Iron Supplement Capsule (Support Optimum Blood Health) 28s … [GREENLIFE] Iron Chelate with FerrochelTM Dietary Supplement Capsule (Gentle on Stomach) 90s … [SANGOFER] Iron Supplement Capsule (Supports Blood Health) 30s … [AFC] Heme Iron Women's Energy & Iron Supplement","accessed":"2026-08-27"},{"id":"iherb_sg_iron","url":"https://sg.iherb.com/search?kw=iron","label":"iHerb Singapore — search 'iron' (retail listings)","quote":"NOW Foods, Iron, 36 mg, 90 Veg Capsules … NOW Foods, Iron, 18 mg, 120 Veg Capsules … Thorne, Iron Bisglycinate, 60 Capsules (25 mg per Capsule) … Solgar, Gentle Iron®, 25 mg, 90 Vegetable Capsules … California Gold Nutrition, Ferrochel® Iron (Bisglycinate), 36 mg, 90 Veggie Capsules","accessed":"2026-08-27"}],"brand_certs":null,"updated_at":"2026-08-29T16:16:23.779398+08:00"},"disclaimer":"kozen-x is not a medical device and does not give medical advice. it lists what published sources have written down. absence of a record is not the same as safe."}