Iron
Also known as: Ferrous sulfate, Ferrous bisglycinate
Iron supports normal red-blood-cell function. It is commonly used when testing shows low iron. Taking iron without a need is discouraged because excess can be harmful. Talk to a professional and consider testing first.
Snapshot
Evidence level is outcome-specific; a supplement can have stronger evidence for one use and limited evidence for another.
What this page can tell you: NIH ODS practicalities for iron — the vitamin C pairing, mineral/medication spacing, the narrow upper limit, and the overdose risk in children.
What it cannot: Whether you need iron or how much — that needs testing and a clinician, since both too little and too much matter. Informational only.
🧩 Stack insights — how this fits into a schedule
Vitamin C — NIH ODS notes vitamin C improves absorption of non-heme (plant/supplement) iron, which is why the two are often taken around the same time. Informational, not a directive to add either.
Calcium and zinc — Iron is commonly spaced away from calcium and zinc because minerals compete for absorption. Review total mineral intake and spacing rather than stacking them at the same time.
Levothyroxine, levodopa, certain antibiotics, PPIs — NIH ODS: iron can interact with levothyroxine, levodopa, and certain antibiotics (reducing their absorption), and acid reducers (PPIs) can lower iron absorption. Space doses apart and confirm timing with a pharmacist.
Overdose / narrow upper limit — NIH ODS: the adult upper limit is 45 mg/day, and iron has a narrow margin — high intakes cause GI upset, and iron overdose is a serious risk, especially in children. Keep iron supplements away from children and don't exceed guidance.
⚠️ Accidental iron overdose in children can be life-threatening — store safely.
Relationship insights are informational only — they describe what is commonly discussed or studied, not what you should take. Not medical advice; review your routine with a clinician or pharmacist.
🧭 How iron caution scales with the amount
| Amount | Caution level | Note |
|---|---|---|
| Amounts within the upper limit (< 45 mg/day) | Moderate | Non-heme iron absorbs better on an empty stomach and with vitamin C; GI upset is common. |
| At/above the upper limit (45 mg/day) | High | NIH ODS adult UL; iron has a narrow margin and excess causes GI and overdose risk. |
Iron overdose (especially in children) is a medical emergency — store safely. Official figures, not a personal recommendation.
🕒 Timing
When: Morning
Food: Empty stomach
Absorbs best on an empty stomach, but a little food is fine if it upsets your stomach. A vitamin C source (or orange juice) improves absorption; coffee, tea, calcium, and dairy within about 1-2 hours reduce it. Some evidence suggests every-other-day dosing absorbs as well as daily with less GI upset - discuss with a professional.
💊 Common use range
Varies — professional-guided mg elemental
Iron can be toxic in excess, especially for children. Use only with professional guidance and keep away from children.
Ranges are informational, not a recommended dose. Talk to a professional about what is right for you.
🤔 Worth considering?
Evidence vs. effort: Strong evidence relative to burden
Clearly useful for correcting a demonstrated deficiency, and iron status can be measured. Supplementing without a known need is commonly discouraged, can upset the stomach, and acute overdose is dangerous, especially for children. Worth confirming a need with a professional first.
A general summary, not a recommendation. Whether something fits your situation is worth discussing with a healthcare professional.
⚠️ Commonly noted interactions (supplements)
Often about absorption or timing rather than danger — separating doses is common. This list is not exhaustive.
🧭 Baseline caution
General caution for ordinary, common use — before accounting for your specific dose, medications, health history, or procedures.
- Narrow margin between enough and too much — easy to overdo
Caution level is an informational summary of commonly discussed caution categories and doses — not a safety rating, approval, or medical advice. Low caution does not mean safe for you.
🔎 Context alerts to review
Context alerts may matter depending on your dose, medications, health history, or procedure plans — they do not mean the supplement is generally risky at ordinary use.
Medications
- Higher caution if you take certain antibiotics (space doses apart)
- Higher caution if you take thyroid medication (space doses apart)
Spacing & absorption
- Mineral spacing — minerals compete for absorption
🩺 Medication caution categories
- Certain antibiotics — Minerals like calcium, iron, magnesium, and zinc can bind certain antibiotics and cut their absorption. The fix is spacing them apart — the exact gap depends on the antibiotic, so ask your pharmacist.
- Thyroid medication — Minerals and fiber can bind thyroid medicine (like levothyroxine) and reduce its absorption when taken together. The usual fix is spacing them several hours apart — confirm with your pharmacist.
🏥 Surgery & procedure caution
Share iron use with your care team; iron status is relevant around surgery.
If you have a procedure scheduled, bring your full supplement list to your surgical and anesthesia team. Do not stop prescribed medication unless your clinician tells you to. Do not start or stop supplements based only on this app.
✅ Quality checklist
- Prefer products with third-party testing or a certificate of analysis (COA).
- Check the label for the exact form and the elemental or active amount per serving.
🧩 Commonly paired with
🔁 Alternatives
None listed.
🗣️ Questions for a professional
- Is Iron appropriate alongside my medications and health history?
- Is there a test or check that would tell us whether I actually need it?
🛡️ Safety notes (source-reviewed)
- NIH ODS adult upper limit: 45 mg/day; high intakes cause GI upset, and overdose is a serious risk — keep away from children.
- Vitamin C improves absorption of non-heme iron; calcium, zinc, and coffee/tea reduce it — spacing matters.
- Interacts with levothyroxine, levodopa, and certain antibiotics; acid reducers (PPIs) lower iron absorption.
⚖️ Evidence limitations
- Iron need is individual; a blood test and clinician guide whether and how much to supplement.
❓ Frequently asked
Should I take iron with vitamin C?
NIH ODS notes vitamin C improves absorption of non-heme (plant/supplement) iron, so the two are commonly taken together. Iron also absorbs better on an empty stomach, though some take it with food to reduce stomach upset.
What should iron be spaced from?
NIH ODS: calcium, zinc, coffee/tea, levothyroxine, and certain antibiotics — take them a few hours apart. A pharmacist can confirm timing.
Is iron dangerous in excess?
Yes — the adult upper limit is 45 mg/day (NIH ODS), iron has a narrow margin, and overdose is a serious risk, especially in children. Keep iron supplements stored safely away from children.
🔬 Evidence snapshot
An essential mineral and a component of hemoglobin that carries oxygen in the blood. Supplementation is used to correct or prevent iron deficiency; routine high-dose use without a known deficiency is not supported and can cause harm.
🧪 Forms & quality
Needs evidence review — no source-reviewed information yet. We only show dose and monitoring details after they have been checked against reputable sources.
See the supplement glossary for what form names like "L-", chelated, or standardized extract mean.
📏 Dose & monitoring
NIH ODS sets an adult (19+) Tolerable Upper Intake Level of 45 mg/day.
Evidence vs. burden: Strong evidence relative to burden
Labs that may be worth discussing: Iron status
Iron status can be measured; supplementing without a known need is commonly discouraged. This may be worth discussing with a healthcare professional.
These are discussion prompts, not required tests. A healthcare professional can advise what makes sense for you.
😐 Commonly reported side effects
- Constipation, nausea, dark stools; toxic in overdose
Non-exhaustive and individual.
🔄 Cycling & breaks
Use is commonly guided by testing rather than fixed cycles.
📅 Daily use notes
Only supplement iron when a need is identified. Separate from calcium, zinc, and magnesium.
📋 Source review status
Source-reviewed — last reviewed 2026-07-02
Placeholder — reinforce test-first and child-safety messaging.
📚 References
- NIH ODS - Iron (Health Professional Fact Sheet)NIH ODS — Verified UL, GI/overdose safety, zinc-absorption note, and interactions (levothyroxine, levodopa, PPIs).
Verified against the source shown. See the research-status page for how review works.
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