Low iron as a man — just my training?
Don't assume so: UK gut specialists say about a third of men and postmenopausal women with iron-deficiency anaemia have an underlying cause, mostly in the gut. A doctor's question.
Main caveat: Not about athletes. Exercise, training load, sport-specific losses and athletic thresholds are absent; using it for athletes is a transfer.
The British Society of Gastroenterology revised its guideline on iron-deficiency anaemia (IDA) in adults through a 13-member committee (gastroenterology, haematology, specialist nursing, two lay members), a formal literature search, GRADE ratings for each statement and three rounds of eDelphi voting.
Anaemia is defined by the laboratory's lower limit, aligned with WHO (haemoglobin below 130 g/L in men, 120 g/L in non-pregnant women), and iron deficiency should be confirmed by iron studies before investigation: serum ferritin is "the single most useful marker", with transferrin saturation helpful when a false-normal ferritin is suspected.
Ferritin under 15 µg/L indicates absent stores (specificity 0.99), under 30 µg/L low stores, laboratories' lower limits sit between 15 and 30, a cut-off of 45 µg/L gives a specificity of 0.92 and may warrant considering GI investigation, and above 150 µg/L absolute iron deficiency is unlikely even with inflammation (in inflammatory bowel disease, up to 100 µg/L may still reflect deficiency).
Because about a third of men and postmenopausal women with IDA have an underlying lesion, mostly in the GI tract, and coeliac disease is found in 3-5%, investigation (urinalysis, coeliac serology, and in men and postmenopausal women gastroscopy and colonoscopy) runs alongside iron replacement; in young women GI pathology is uncommon and, after coeliac screening, endoscopy is reserved for features of concern.
Treatment starts with one tablet a day of a ferrous salt, fasting, every other day if not tolerated, with an early haemoglobin check and about 3 months of continuation after it normalises; vitamin C with the tablet is not recommended; parenteral iron is for contraindication, failure, intolerance or urgency.
For non-anaemic iron deficiency the efficacy of treatment is unclear, objective capacity did not improve in a meta-analysis, fatigue may, and treatment is "reasonable" if symptomatic.
Our reading: the base's source for when iron deficiency is a doctor's question and for the clinical first-line dose; its numbers answer a gastroenterologist's questions, so an athlete's ferritin is read with this purpose in mind.
Protocol
Process: commissioned by the BSG in 2018; BSG guideline process (revised 2018) and AGREE II; literature search by the National Guidelines Centre on "iron deficiency anaemia"; section leads drafted statements; three rounds of anonymised eDelphi voting in 2020, adopted above 80% consensus; evidence quality (GRADE: high, moderate, low, very low) and statement strength (strong, weak) rated by section leads and ratified by the co-chairs; approved by the BSG Clinical Services and Standards Committee.
Scope: adults with IDA in primary and secondary care in the UK; n = not applicable (guideline).
Funding: "The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors."
Competing interests (as printed): ILPB: Vifor advisory board, Pharmcosmos advisory board; PI for Feraccru studies. RL: Vifor Advisory Board, NHS England advisor. MP: Trio Medicines (research funding); IPSEN, Advanced Accelerator Applications, Mayoly Spindler laboratories (consultancies). The other nine authors: none declared.(Not printed in the paper, our note: Vifor and Pharmacosmos market intravenous iron, and Feraccru is the brand name of ferric maltol, which the guideline discusses.)
Key Results
Selected statements with the guideline's own grading (executive summary):
| Statement | Evidence | Consensus | Strength |
|---|---|---|---|
| Ferritin the single most useful marker of IDA; transferrin saturation if a false-normal ferritin is suspected | medium | 92% | strong |
| A haemoglobin rise ≥10 g/L within 2 weeks of iron is highly suggestive of absolute iron deficiency | medium | 100% | strong |
| Initial investigation of confirmed IDA: urinalysis, coeliac screening and, in appropriate cases, upper and lower GI endoscopy | moderate | 85% | strong |
| Coeliac disease in 3-5% of IDA; screen routinely | high | 84% | strong |
| GI cancer risk in iron deficiency without anaemia is low | high | 92% | strong |
| Men and postmenopausal women with new IDA: gastroscopy and colonoscopy first line | moderate | 100% | strong |
| One tablet a day of ferrous sulphate, fumarate or gluconate; if not tolerated, one every other day, another oral preparation or parenteral iron | medium | 92% | strong |
| Check the haemoglobin response in the first 4 weeks; continue about 3 months after haemoglobin normalises | medium | 92% | strong |
| Parenteral iron when oral iron is contraindicated, ineffective or not tolerated, or correction is urgent | high | 92% | strong |
| Non-anaemic iron deficiency: invasive investigation not supported without additional indications; periodic blood counts | low | 92% | weak |
| Young women: GI pathology uncommon; after coeliac screening, investigate only with features of concern | moderate | 92% | strong |
| Young men with confirmed IDA: same algorithm as older people | moderate | 100% | strong |
Ferritin, in the guideline's words (Definitions): under 15 µg/L "indicative of absent iron stores" (specificity 0.99); under 30 µg/L "generally indicative of low body iron stores"; laboratory lower limits 15-30 µg/L; 45 µg/L "the optimal trade-off between sensitivity and specificity" (specificity 0.92), "figures below this may warrant consideration of GI investigation"; above 150 µg/L "unlikely to occur with absolute iron deficiency, even in the presence of inflammation".In the IBD section: up to 100 µg/L with inflammation "may still reflect iron deficiency".
Who to investigate: "investigation should be considered at any level of anaemia in the presence of iron deficiency"; for non-anaemic iron deficiency GI investigation is generally not warranted in premenopausal women, but "the threshold for investigation of NAID should however be low in men, postmenopausal women, and those with GI symptoms or a family history of GI pathology".Endoscopy in premenopausal women with IDA if over 50, not menstruating, red-flag symptoms, a strong family history, or IDA disproportionate to menstrual losses. IDA prevalence in healthy premenopausal women 5-12%.
Taking oral iron: iron with meals can cut bioavailability by up to 75%, so fasting or between meals; tea's inhibitory effect "dissipates within 60 min"; "coadministration of vitamin C with oral IRT is not recommended" (a large RCT found no gain in haematological response, iron loading or side effects); modified-release preparations not recommended.
Dose and schedule (evidence cited): doses of 60 mg raise hepcidin for 24 hours and cut the next absorption by 35-45% (REF-1415), so 60 mg once a day absorbed about as much as 60 mg twice a day; alternate-day dosing raised fractional and total absorption in iron-depleted women, 200 mg on alternate days giving almost twice the absorption of 100 mg on consecutive days; in IDA, 60 mg twice daily raised haemoglobin faster than 120 mg on alternate days, with similar rises after the same total dose and less nausea.Conclusion: "a once daily dose of 50–100 mg of elemental iron (eg, one ferrous sulfate 200 mg tablet a day) taken in the fasting state may be the best compromise option for initial treatment".
Response: 72.8% of patients in pooled trial data had an adequate haemoglobin response within 2 weeks; no rise of at least 10 g/L after 2 weeks predicted failure (sensitivity 90.1%, specificity 79.3%); a 28-day review may suit alternate-day regimens.
Side effects: GI effects with ferrous sulphate vs placebo OR 2.32 (95% CI 1.74 to 3.08), vs parenteral iron OR 3.05 (2.07 to 4.48), with no dose-effect relationship over 50-400 mg a day; trial discontinuation 0-24%, up to 40% in observational studies.
Parenteral iron: replenishes stores faster but the haemoglobin response is typically similar; infusion reactions about 0.5%; hypophosphataemia with ferric carboxymaltose 58%, iron derisomaltose 4%, iron sucrose 1%; UK regulator advice (2020) to monitor phosphate in those at risk.
Non-anaemic iron deficiency: treatment efficacy "unclear"; a meta-analysis the guideline cites found no improvement in VO2max or RERmax; subjective fatigue, mental quality of life and cognition may improve in premenopausal women; treatment "reasonable" if symptomatic.
Monitoring: haemoglobin about every 4 weeks until normal, then a blood count 3-monthly for 12 months and 6-monthly for 2-3 years; "insufficient data to recommend routine ferritin monitoring".
Mechanisms
Measured (studies cited): oral iron raises hepcidin, which follows a diurnal pattern, and lowers absorption of the next dose; food lowers absorption of iron salts.
Authors' interpretation: in functional iron deficiency (inflammation, chronic disease) hepcidin restricts supply despite normal stores, so ferritin can look normal while iron is unavailable; transferrin saturation below 20% indicates iron restriction.
Practical Application
Low iron as a man — just my training? Don't assume so: UK gut specialists say about a third of men and postmenopausal women with iron-deficiency anaemia have an underlying cause, mostly in the gut. A doctor's question.
When it is a doctor's question (A, guideline; transfer): any anaemia with iron deficiency; non-anaemic iron deficiency in a man, a postmenopausal woman, or anyone with GI symptoms or a family history of GI disease; IDA in a young woman out of proportion to her periods. Not from this paper; the base's own practice: the assistant names the finding and refers; it does not diagnose or name a cause.
Ferritin cut-offs with their purpose: 15 (absent), 30 (low), 45 (a trade-off for whether to investigate), 150 (absolute deficiency unlikely), up to 100 with inflammation in IBD — numbers for clinical decisions in anaemic adults; the sports-medicine cut-off for athletes is REF-1410's 30, read with CRP.
Vitamin C — a wording conflict with the base: "coadministration of vitamin C with oral IRT is not recommended", while the base's own practice lines in SYNTH-06 and REF-340 say to take iron "with vitamin C". Proposed fix for those owners: vitamin C is not needed with a tablet; vitamin C-rich food helps iron from plant meals (REF-1410).
Every other day is the guideline's step when daily iron is not tolerated; REF-1416 shows it gives the same ferritin at the same total dose with fewer GI effects, over twice the time.
Tea and food: keep tea away from the dose (its effect fades within about 60 min) and take the tablet fasting or between meals (food can cut absorption by up to 75%).
Fatigue without anaemia: treatment "reasonable" if symptomatic, which matches REF-1412 (fatigue may ease, capacity not shown).
IV iron: for contraindication, failure, intolerance or urgency, a clinician's decision; hypophosphataemia is common with one formulation (58%).
Limitations
Not about athletes. Exercise, training load, sport-specific losses and athletic thresholds are absent; using it for athletes is a transfer.
Evidence behind statements varies. Several strong recommendations rest on low or very low evidence (for example, monitoring every 6 months: very low), where strength reflects consensus and judgement.
Gastroenterology lens. The thresholds are tuned to finding GI disease in anaemic adults.
UK context. Products, costs and referral pathways are British (February 2021).
Competing interests. Two of 12 authors report advisory roles with intravenous-iron companies (Vifor; Pharmacosmos, printed "Pharmcosmos") and one is PI for ferric maltol (Feraccru) studies; no funding was declared.
How this entry was checked and changed
Why this level
a major national guideline with graded, voted statements (rubric: major consensus / position statement), read from the full text (Europe PMC, CC BY-NC 4.0). The level is the document's: the evidence behind individual statements ranges from high to very low, and the guideline is written for adults with iron-deficiency anaemia in UK health care, so its use for athletes is a transfer
Full text (checked 2026-10-28)
Approximately a third of men and postmenopausal women presenting with IDA have an underlying pathological abnormality, most commonly in the GI tract (full text)
Serum ferritin is the single most useful marker of IDA (evidence quality—medium, consensus—92%, statement strength—strong) (full text)
An SF level of <15 µg/L is indicative of absent iron stores, while SF levels of less than 30 µg/L are generally indicative of low body iron stores; the lower limit of normal for most laboratories lies in the range 15–30 µg/L (full text)
A cut-off of 45 µg/L provides a respectable specificity of 0.92; an SF value above 150 µg/L is unlikely to occur with absolute iron deficiency, even in the presence of inflammation (full text)
SF levels of up to 100 µg/L in the presence of inflammation may still reflect iron deficiency (IBD section) (full text)
CD is found in 3%–5% of cases of IDA (full text)
The threshold for investigation of NAID should however be low in men, postmenopausal women, and those with GI symptoms or a family history of GI pathology (full text)
A once daily dose of 50–100 mg of elemental iron taken in the fasting state may be the best compromise option for initial treatment (full text)
Coadministration of vitamin C with oral IRT is not recommended; the inhibitory effect of tea on iron absorption dissipates within 60 min (full text)
Treatment should be continued for a period of around 3 months after normalisation of the Hb level (full text)
GI side effects with oral ferrous sulfate vs placebo (OR 2.32 (95% CI 1.74 to 3.08)); hypophosphataemia with ferric carboxymaltose (58%), iron derisomaltose (4%), iron sucrose (1%) (full text)
It would be reasonable to offer treatment for NAID if symptomatic (full text)
Competing interests: ILPB: Vifor advisory board, Pharmcosmos advisory board; PI for Feraccru studies. RL: Vifor Advisory Board (full text)