Iron
Iron is an essential trace mineral the body uses to make haemoglobin in red blood cells, which carry oxygen, and for energy production in every cell. UK NHS reference intakes are 8.7 mg/day for men, 14.8 mg/day for menstruating women, and 8.7 mg/day for women after the menopause.
Camden Medicals editorial · Last reviewed 12 June 2026 · Next review June 2027
- Cross-checked against
- NHS
- NICE
- BNF
- EFSA
- FSA
Camden's editorial team independently graded each health claim below on the strength of the published evidence — see the grade beside every condition.
- Class
- Mineral
- Typical daily dose
- For diagnosed iron-deficiency anaemia, NICE CKS / BSG guidance is one tablet daily of ferrous sulfate (200 mg ≈ 65 mg elemental iron), ferrous fumarate (210 mg ≈ 65 mg elemental), or two tablets daily of ferrous gluconate (300 mg ≈ 35 mg elemental each). Treatment is guided by clinical response and continued for ~3 months after haemoglobin normalises to replenish stores.
- Top use evidence
- Strong
On this page
What it is
Iron is an essential trace mineral and the most abundant transition metal in the body. It exists in two oxidation states relevant to nutrition — ferrous (Fe²⁺) and ferric (Fe³⁺) — and switches between them in many biological reactions.
Dietary iron comes in two forms with very different absorption profiles. Haem iron, found in meat, poultry, and seafood, is absorbed at roughly 15–35%. Non-haem iron, found in plants, beans, fortified cereals, and eggs, is absorbed at 2–20% depending on the meal: vitamin C and meat boost it, while tea, coffee, calcium, and phytates from whole grains block it.
UK supplements come in several common forms. Ferrous (Fe²⁺) salts — ferrous sulfate, ferrous fumarate, and ferrous gluconate — are the standard NHS treatment forms for iron-deficiency anaemia and contain different amounts of elemental iron per tablet. Ferrous bisglycinate (a chelated form, sometimes marketed as "gentle iron"), iron protein succinylate, and ferric pyrophosphate are alternative supplemental forms often chosen for tolerability or palatability rather than for greater proven efficacy.
At a glance
- UK NHS RNI: 8.7 mg/day for adult men and post-menopausal women, 14.8 mg/day for women aged 19–49.
- Iron from animal foods (haem) is absorbed two to three times more efficiently than iron from plant foods (non-haem).
- Iron supplements are useful for diagnosed iron deficiency or low iron stores; routine supplementation in iron-replete adults has not been shown to improve energy or wellbeing.
- Recent dosing research (Stoffel 2017) suggests alternate-day single morning doses are absorbed more efficiently and cause fewer side effects than the older "twice daily with vitamin C" pattern.
- Iron supplements are a leading historical cause of paediatric overdose poisoning. Keep them locked away from children.
What people use it for
Menstruating women (especially with heavier-than-average periods)
Menstrual blood loss is the commonest cause of low iron stores in UK adults of reproductive age. Daily iron supplementation in menstruating women reduces the risk of anaemia, raises haemoglobin and iron stores, and reduces symptomatic fatigue (Low/Pasricha 2016 Cochrane). [9,1]
Some evidenceStrongPregnant women with diagnosed iron deficiency or anaemia
Iron supplementation corrects deficiency and lowers the risk of maternal anaemia. NHS guidance is that pregnant women should not routinely take iron supplements unless advised by a midwife or GP — pregnancy iron status is checked at antenatal blood tests. [1,10]
Some evidenceStrongVegetarians and vegans
Plant iron (non-haem) is absorbed less efficiently than meat iron. The NIH ODS notes the iron requirement is roughly 1.8× higher for vegetarians than for meat-eaters. Pairing iron-rich plant foods with vitamin C (e.g. peppers, citrus) at the same meal increases absorption. [6]
Some evidenceModerateEndurance athletes (runners, especially women)
Distance running can deplete iron stores through foot-strike haemolysis, gut iron loss, and sweat. In iron-deficient (low-ferritin) athletes — anaemic or non-anaemic — supplementation improves measures of exercise performance and symptomatic fatigue. In iron-replete athletes, evidence of benefit is weak. [9]
Some evidenceModerateFrequent blood donors
Each whole-blood donation removes ~200–250 mg of iron. Some UK transfusion services advise iron-replacement supplementation between donations for at-risk donors. Discuss with the donor service if recovery times feel slow or you become anaemic. [6]
Some evidenceModerateAdults with restless legs syndrome (RLS) and low ferritin
Where serum ferritin is ≤75 µg/L, oral iron (~65 mg elemental once daily) is "possibly effective" for RLS in adults per the IRLSSG 2018 evidence-based and consensus guidelines. RLS treatment is a clinical decision — speak to a GP rather than self-treating. [11,12,13]
Some evidenceModerate
How it works
Iron sits at the centre of the haem ring inside haemoglobin and myoglobin, where it binds and releases oxygen, and at the active site of cytochromes in the mitochondrial electron-transport chain that generate ATP.
Common myths
Myth"Iron supplements stop period symptoms"
RealityIron supplements correct iron deficiency caused by menstrual blood loss; they do not change the periods themselves, which depend on hormonal and anatomical factors. If heavy menstrual bleeding is causing recurrent low iron, the bleeding is the upstream issue — speak to a GP about NICE-recognised treatments for heavy menstrual bleeding (NICE NG88). Iron is part of the picture, not the whole treatment. [9]
Myth"If you feel tired, you must be low in iron"
RealityFatigue has many causes; iron deficiency is one of them. Many people with mild iron deficiency are not noticeably fatigued, and many people who are fatigued have normal iron stores. The Low/Pasricha 2016 Cochrane review found that supplementation reduced symptomatic fatigue specifically in menstruating women, not in iron-replete people. Get a blood test (full blood count + ferritin) before self-treating chronic fatigue with iron. [9]
Myth""Gentle iron" (bisglycinate) does not cause constipation"
RealityBisglycinate is associated with fewer GI side effects than ferrous sulfate in head-to-head trials, but "fewer" is not "none". The head-to-head evidence base is also smaller and lower-quality than marketing language implies. People who do not tolerate ferrous sulfate often do better on bisglycinate; this is reasonable. The leap from "better tolerated" to "no side effects" is not evidence-based. [14]
Myth"You cannot overdose on iron from food"
RealityFor most healthy adults, iron from food is self-regulated and very unlikely to cause overdose. The same is NOT true for iron tablets: adult-strength iron supplements have historically been a leading cause of paediatric overdose fatalities. People with the genetic condition haemochromatosis can also accumulate iron from ordinary food and supplements, with serious long-term consequences if untreated. The blanket statement "you cannot overdose" applies narrowly and ignores the children-and-haemochromatosis exceptions. [1]
Common online questions
Synthesised from the questions UK shoppers most often ask online about Iron. Each answer is editorial and links to its evidence in the Sources list below.
Should I take iron in the morning or the evening?
Morning, on an empty stomach, is the standard recommendation — absorption is highest then. Stoffel 2017 (Lancet Haematol) showed that giving iron as a single morning dose (rather than splitting it across the day) improves fractional absorption, because the first dose suppresses absorption of subsequent doses via the iron-regulating hormone hepcidin. If iron upsets your stomach when taken alone, taking it with a small amount of food is acceptable; absorption falls by roughly 40% but the dose you actually keep down is the dose that counts. [15]
Should I take vitamin C with my iron supplement every day?
The traditional advice — "take iron with vitamin C or orange juice" — is based on Hallberg-era studies showing vitamin C increases non-haem iron absorption from a meal. The picture has been complicated by the Stoffel 2017 dosing work showing that alternate-day dosing achieves better cumulative absorption than daily dosing, regardless of vitamin C. The practical position: vitamin C does not hurt and may help on the days you do dose; the bigger lever is the dosing schedule itself. NICE CKS recommends taking iron with a vitamin-C drink if tolerated, and offers alternate-day dosing as an option for people who get side effects. [15,3]
Do I need to take iron with food, or on an empty stomach?
Empty stomach absorbs more — roughly 40% more by classic absorption studies — but is more likely to cause nausea or cramping. Many people end up on a "with a small snack" compromise. Calcium-rich foods (milk, yoghurt), tea, coffee, and certain wholegrain breads block iron absorption noticeably; keep these away from your iron dose by at least an hour. Antacids and proton-pump inhibitors also reduce absorption. [3]
Is liquid iron better than tablets?
Liquid iron preparations (often ferrous sulfate or ferrous gluconate solutions) deliver the same active ingredient as tablets and are absorbed similarly. Liquids are useful for people who cannot swallow tablets, for paediatric dosing, or when very low doses are needed; they often stain teeth, so use a straw or rinse afterwards. There is no consistent evidence that liquid iron is better tolerated than tablets at equivalent elemental doses. [3]
Is "gentle iron" (ferrous bisglycinate) really gentler on the stomach?
Bisglycinate is a chelated form of iron in which two glycine amino acids surround the iron ion. The marketing case is that it is absorbed without releasing free Fe²⁺ in the gut, so it causes less GI irritation. Smaller head-to-head trials and observational data tend to support better tolerability, but the evidence base is much weaker than the marketing implies — most comparisons are short, small, and industry-linked. Ferrous bisglycinate is a reasonable option if ferrous sulfate upsets your stomach. It is typically more expensive per elemental milligram of iron. [14]
Can iron tablets cause black stools? Is that bleeding?
Dark or black stools are a normal, expected effect of oral iron — unabsorbed iron passes through the gut and darkens the stool. This is benign and reverses when you stop. The colour also looks similar to the tarry stools of an upper-GI bleed, which is a medical emergency. If you notice fresh red blood, a sticky tar-like consistency, dizziness, or unexplained weight loss alongside the dark colour, contact your GP — it may not be the iron. [2]
Are iron tablets dangerous if a child swallows them?
Yes, very. Iron supplements have historically been one of the leading causes of poisoning death in children in the United States and the UK. Adult-strength iron tablets look like sweets to a small child. Always store them in a child-resistant container in a locked or high cupboard, and never call them "vitamins" in front of children. If a child has swallowed any iron tablets, contact NHS 111 or A&E immediately even if they seem well — symptoms can be delayed. [2]
⚖️ The official position
What may lawfully be claimed about Iron in Great Britain. This is a regulatory position, not an evidence grade.
A health claim is authorised in Great Britain.
“Iron contributes to normal formation of red blood cells and haemoglobin”
“Iron contributes to the reduction of tiredness and fatigue”
“Iron contributes to normal oxygen transport in the body”
“Iron contributes to normal cognitive function”
“Iron contributes to normal cognitive development of children”
“Iron contributes to normal energy-yielding metabolism”
“Iron contributes to the normal function of the immune system”
This claim is authorised for use in Great Britain under the GB Nutrition and Health Claims regulation. A product may carry it when it provides at least 15% of the UK NRV per recommended daily portion.
Authorised UK health claims
Verbatim from the GB Nutrition and Health Claims Register (Reg 432/2012 as assimilated in GB). A product can carry these claims when it provides at least 15% of the UK NRV per recommended daily portion.
7 authorised claims — show / hide
- "Iron contributes to normal formation of red blood cells and haemoglobin"
- "Iron contributes to the reduction of tiredness and fatigue"
- "Iron contributes to normal oxygen transport in the body"
- "Iron contributes to normal cognitive function"
- "Iron contributes to normal cognitive development of children"
- "Iron contributes to normal energy-yielding metabolism"
- "Iron contributes to the normal function of the immune system"
Camden guides citing Iron
Editorial pieces from the Camden blog that reference Iron. Each guide cites the evidence it draws on.
🔬 Camden’s evidence review
The research Camden reviewed, graded on its strength. This is our own appraisal — it sits beneath the official guidance above, never above it.
Iron-deficiency anaemia (treatment, alongside dietary change and identifying the cause)
StrongEvidencestrongOral iron is the standard first-line treatment for iron-deficiency anaemia in adults, per the British Society of Gastroenterology 2021 guidelines and NICE Clinical Knowledge Summaries. Diagnosis (full blood count + ferritin) and a parallel investigation of the cause of iron loss are essential — IDA can be the first sign of gastrointestinal pathology including malignancy in older adults. Self-supplementation does not replace the diagnostic workup. [16,17,3]
Restless legs syndrome (RLS) with low ferritin
ModerateEvidencemoderateThe International Restless Legs Syndrome Study Group 2018 task force review (Allen et al., Sleep Medicine) found oral iron at 65 mg elemental once daily "possibly effective" for adults with serum ferritin ≤75 µg/L. Intravenous ferric carboxymaltose has stronger evidence (Class I) for moderate-to-severe RLS. Iron supplementation for RLS without the ferritin gate is not supported. [11,12,13]
Symptomatic fatigue and exercise performance in menstruating women
ModerateEvidencemoderateThe 2016 Cochrane review (Low, Speedy, Styles, De-Regil, Pasricha — CD009747.pub2) of 67 trials in 8,506 menstruating women found that daily oral iron supplementation reduced anaemia, raised haemoglobin and iron stores, improved maximal and submaximal exercise performance, and reduced symptomatic fatigue. Cognitive-performance evidence was inconsistent across trials. [9]
Routine iron supplementation in iron-replete adults (general energy / wellness)
InsufficientEvidenceinsufficientMarketing for iron supplements often implies a general energy benefit in adults without iron deficiency. The Cochrane evidence in menstruating women applies primarily to those with low or borderline-low iron stores; blanket supplementation in iron-replete adults has not been shown to produce energy or wellbeing gains and carries unnecessary side-effect risk. [9,1]
Routine antenatal iron supplementation in non-anaemic pregnant women
MixedEvidencemixedUK NHS guidance does not routinely recommend iron supplements during pregnancy unless iron status is low — pregnancy iron is monitored through antenatal blood tests. International guidance varies: a 2025 systematic review (Watt et al., Family Practice) of 23 studies in 4,492 non-anaemic pregnant women found that prophylactic iron raised haemoglobin and ferritin and reduced the risk of anaemia (NNT=10), with no detected differences in birth weight, preterm birth, or caesarean rate; harms data was poor-quality. The benefits and harms balance for non-anaemic women is an active question. [10,1]
Gastrointestinal side effects of ferrous sulfate (the standard NHS treatment salt)
StrongEvidencestrongTolkien et al. 2015 (PLoS One) meta-analysed 43 trials in 6,831 adults and found ferrous sulfate roughly doubled the odds of GI side effects compared with placebo (OR 2.32, 95% CI 1.74–3.08) and tripled them compared with intravenous iron (OR 3.05, 95% CI 2.07–4.48). The relationship was not dose-dependent across the trials. This is the clinical reality behind why some people stop iron tablets. [14,18]
Safety
Iron supplements are appropriate when iron stores are low or for groups at higher risk of low iron (such as menstruating women on a low-iron diet). For most iron-replete adults they are unnecessary. They are not benign in everyone — keep them locked away from children, and do not take them if you have an iron-overload condition.
Talk to your pharmacist or GP first if you:
- You have haemochromatosis, thalassaemia, sickle-cell disease, or any other iron-overload condition.
- You have inflammatory bowel disease (Crohn's, ulcerative colitis) — oral iron tolerability and absorption can be poor; intravenous iron may be more appropriate.
- You have ever had an iron-tablet overdose in the household, or you have small children at home — adult-strength iron is a leading historical cause of paediatric poisoning fatalities.
- You take levothyroxine, a tetracycline or quinolone antibiotic, methyldopa, levodopa, mycophenolate, a bisphosphonate, an antacid, or a proton-pump inhibitor (PPI) — iron interacts with all of these.
- You are pregnant or breastfeeding — NHS guidance is not to routinely supplement; iron status is checked at antenatal blood tests.
- Your stools are unexpectedly black or tarry alongside other symptoms (dizziness, fresh blood, weight loss) — iron darkens stool, but so does upper-GI bleeding, and the two can be confused.
- You have ongoing fatigue you suspect is anaemia — get a blood test (full blood count + ferritin) rather than self-treating.
Common side effects: Constipation, nausea, abdominal pain, and dark stools are common with ferrous-salt iron tablets and are dose-related. Dark stools are expected and not a sign of bleeding. Side effects often improve with alternate-day dosing or a switch to ferrous bisglycinate.
Pregnancy and breastfeeding
NHS guidance is that pregnant women should NOT routinely take iron supplements; iron status is checked at antenatal blood tests and supplementation initiated where clinically indicated. Where iron supplementation is started in pregnancy, it is on the advice of a midwife or GP and continued under their guidance. International guidance varies — some countries do recommend routine antenatal supplementation. Speak to your midwife or GP rather than self-starting.
NHS guidance does not routinely recommend iron supplements during breastfeeding for women whose iron status is normal. Speak to your GP or pharmacist if you suspect low iron post-partum.
Talk to your GP, midwife, or pharmacist before starting any supplement during pregnancy or breastfeeding.
More clinical detail (for clinicians and informed readers)
Contraindications
- Haemochromatosis or other iron-overload conditions — supplemental iron is contraindicated unless specifically advised by a haematologist.
- Active peptic ulcer disease — discuss with prescriber; oral iron may aggravate symptoms.
- Repeated blood transfusions (transfusion-related iron overload) — supplemental iron contraindicated.
Drug interactions
- Levothyroxine — separate doses by at least 4 hours (iron chelates thyroxine and reduces absorption; BNF Appendix 1).
- Tetracycline antibiotics (doxycycline, lymecycline) — separate doses by 2–3 hours; absorption of both reduced.
- Quinolone antibiotics (ciprofloxacin, levofloxacin, ofloxacin) — separate doses by 2 hours.
- Methyldopa — iron reduces methyldopa absorption; separate doses.
- Levodopa (and carbidopa-levodopa) — iron reduces absorption; separate doses.
- Mycophenolate — concurrent iron reduces mycophenolate absorption; avoid concurrent dosing.
- Bisphosphonates (alendronate, risedronate) — separate doses by at least 2 hours.
- Antacids (containing magnesium, aluminium, calcium) — reduce iron absorption; separate doses.
- Proton-pump inhibitors (omeprazole, lansoprazole) and H2-receptor antagonists — reduce iron absorption by raising gastric pH; consider clinical relevance.
- Calcium supplements — reduce non-haem iron absorption when taken in the same meal; separate doses.
This is not an exhaustive list. Always tell your prescriber and pharmacist about every supplement you take.
Common side effects
- Constipation — the most common reason people stop iron tablets.
- Nausea, abdominal pain, heartburn.
- Diarrhoea.
- Dark or black stools — expected; reverses on stopping; not GI bleeding.
- Tooth staining with liquid iron preparations — use a straw or rinse afterwards.
Rare side effects
- Severe vomiting, severe abdominal pain, haematemesis, or signs of GI bleeding — stop iron and seek medical advice urgently.
- Iron overload from prolonged high-dose supplementation in undiagnosed haemochromatosis.
- Acute iron poisoning following accidental overdose — particularly in children. A medical emergency: contact NHS 111 or A&E immediately.
How to take it
- UK Reference Nutrient Intake
- Typical supplemental range
- For diagnosed iron-deficiency anaemia, NICE CKS / BSG guidance is one tablet daily of ferrous sulfate (200 mg ≈ 65 mg elemental iron), ferrous fumarate (210 mg ≈ 65 mg elemental), or two tablets daily of ferrous gluconate (300 mg ≈ 35 mg elemental each). Treatment is guided by clinical response and continued for ~3 months after haemoglobin normalises to replenish stores.
- Timing
- Morning, on an empty stomach, gives the highest absorption. Recent evidence (Stoffel 2017) suggests alternate-day single morning doses improve cumulative absorption versus daily dosing in iron-depleted women, because daily dosing raises hepcidin and damps absorption of the next dose. NICE CKS lists alternate-day dosing as a recognised option for people who do not tolerate daily dosing.
How to spot quality
Look for
- A named ferrous (Fe²⁺) form: ferrous sulfate, ferrous fumarate, ferrous gluconate, or ferrous bisglycinate (chelated). Or, where Fe³⁺ is used (e.g. ferric pyrophosphate in gummies), the form is named explicitly.
- Elemental iron amount stated alongside the compound mass and as % NRV (e.g. "ferrous bisglycinate providing 14 mg elemental iron, 100% NRV").
- GMP-certified manufacture; ideally third-party verification of declared iron content.
- Child-resistant container — non-negotiable for adult-strength iron.
Red flags
- "Iron complex" or "iron blend" with no elemental iron amount in mg.
- "Energy-boosting iron" framing — energy/fatigue claims attach to deficiency correction, not blanket use in iron-replete adults.
- Co-supplemented with calcium, green tea extract, or coffee/caffeine — these reduce iron absorption from the same dose.
- Sweet-shaped chewables or gummies in adult-strength iron without a child-resistant container.
- Marketing claims that iron is a remedy for heavy periods, hair loss, restless legs, or fatigue at a population level — these are diagnosis-led conditions, not consumer-supplement promises.
Where Camden lands · meets the bar
Camden's NB-510 (Iron and Vitamin C Gummies) declares 7 mg elemental iron per gummy (50% NRV) as ferric pyrophosphate in sunflower lecithin, plus 20 mg vitamin C as ascorbic acid. Directions are 1 gummy daily (children 3+ and adults) or 2 for menstruating-female adults — two gummies provide 14 mg, effectively at the 14.8 mg/day RNI from supplement alone. Form and elemental amount are named on the label. For diagnosed iron-deficiency anaemia, treatment doses are higher than any food-supplement gummy and should come from a GP-prescribed ferrous-salt tablet.
Commonly combined with
Other ingredients that share a biological pathway, cofactor relationship, or evidence-backed protocol with this one. Mechanisms below cite primary physiology — not folk pairing. Doses are literature ranges, not recommendations. Talk to your pharmacist or GP before changing your stack, especially if you take prescription medication.
Vitamin C
Strong evidenceVitamin C reduces ferric iron to the absorbable ferrous form — a classic enhancer of plant iron uptake.
Non-haem iron enters enterocytes as the ferrous (Fe²⁺) form via DMT1, but most dietary non-haem iron is ferric (Fe³⁺). Vitamin C reduces ferric to ferrous iron in the stomach and forms a soluble chelate that survives the higher duodenal pH where absorption occurs. Effect is robust for non-haem iron from plants and oral ferrous-sulfate supplements; haem iron from meat uses a different pathway and is less affected. Recent guidance (Stoffel 2017) suggests alternate-day single morning doses absorb more efficiently than twice-daily-with-vitamin-C dosing, because morning hepcidin rise blunts the afternoon dose.
Evidence: Hallberg & Hulthén 2000 (Am J Clin Nutr) is the canonical dose-response paper. Li 2020 (JAMA Netw Open) found no benefit of adding vitamin C to oral iron versus iron alone in the supplemental setting — the strong evidence is for food-iron, not supplement-iron. [19,20,15]
Doses studied: 100 mg vitamin C with 18–65 mg iron at the same meal for food-iron absorption; alternate-day morning dosing for supplements per Stoffel 2017
Found in Camden: Iron & Vitamin C Gummies 7mg 150 Gummies
Vitamin B12
Moderate evidenceIron and B12 are the two most commonly co-deficient nutrients in vegan and vegetarian diets; both are needed for red-cell production.
Iron is incorporated into haemoglobin and is rate-limiting for erythropoiesis when intake is low. Vitamin B12 is required for DNA synthesis in red cell precursors; deficiency produces megaloblastic (macrocytic) anaemia. When iron deficiency (microcytic, low MCV) and B12 deficiency (macrocytic, high MCV) coexist, the mean cell volume can normalise, hiding the dual deficiency on routine FBC. This is most relevant in vegans and long-term vegetarians, where B12 intake is low (animal-source-only at clinically meaningful doses) and non-heme iron is less bioavailable. Co-supplementation is appropriate where both deficits are confirmed.
Evidence: Pawlak 2014 (Eur J Clin Nutr 68:541) systematic review found B12 deficiency prevalence of 0-86.5% across vegan and vegetarian populations, with vegans at highest risk. Iron deficiency prevalence in vegans/vegetarians is similarly elevated in surveys despite total iron intake often being adequate, due to lower non-heme bioavailability. Combined screening is supported by multiple national dietetic society guidelines. [21,22]
Doses studied: Routine RNI: 8.7 mg iron (men/post-menopausal women) or 14.8 mg (premenopausal women) + 2.5 ug B12. Confirmed deficiency requires individualised dosing under healthcare-professional supervision.
Chlorella (Chlorella vulgaris, Chlorella pyrenoidosa)
Limited evidencePlant-based iron-and-protein cluster — chlorella contributes both protein and modest iron; vitamin C combined with iron-containing meals supports absorption.
Chlorella is approximately 50-60% protein by dry weight and contains roughly 130-180 mg iron / 100 g dry weight (in non-heme form, with moderate bioavailability). The protein-iron contribution to a plant-based diet is real but modest at typical 3-6 g/day dosing — about 4-11 mg iron per serving, of which a smaller fraction is bioavailable.
Vitamin C combined with iron-containing meals enhances non-heme iron absorption. The pairing is dietary rather than supplement-tier.
Diagnosed iron-deficiency anaemia requires therapeutic iron (ferrous sulphate / ferrous fumarate / ferrous bisglycinate at therapeutic doses) via the GP, not chlorella.
Evidence: Mechanism well-established. No specific combination trial evidence on clinical endpoints. [5]
Doses studied: 3-6 g/day chlorella alongside vitamin-C-containing foods. Therapeutic iron supplementation for diagnosed deficiency is a separate clinical context.
Spirulina (Arthrospira platensis, Arthrospira maxima)
Limited evidencePlant-based iron-and-protein cluster — spirulina contributes both protein and modest iron; vitamin C combined with iron-containing meals supports absorption.
Spirulina is approximately 60-70% protein by dry weight and contains roughly 28-40 mg iron / 100 g dry weight (in non-heme form, with moderate bioavailability). The protein-iron contribution to a plant-based diet is real but modest at typical 3-6 g/day spirulina dosing — about 1-3 mg iron per serving.
Vitamin C combined with iron-containing meals enhances non-heme iron absorption (by reducing ferric to ferrous form and counteracting phytate / polyphenol absorption inhibition). The pairing is dietary rather than supplement-tier.
The combination is mechanism-supportive — spirulina contributes plant-protein and modest iron; a properly composed plant-based diet plus iron-rich foods at NHS Eatwell-Guide intake levels meets requirements without therapeutic-iron-level supplementation. Diagnosed iron-deficiency anaemia requires therapeutic iron via the GP, not spirulina.
Evidence: Mechanism well-established. No specific combination trial evidence on clinical endpoints. [5]
Doses studied: 3-6 g/day spirulina alongside vitamin-C-containing foods (citrus, peppers, broccoli, kiwi). Therapeutic iron supplementation for diagnosed deficiency is a separate clinical context.
Vitamin B2 (Riboflavin)
Moderate evidenceIron-metabolism pairing — B2 supports normal iron metabolism (UK Article 13.1).
B2 cofactor for ferritin transport + iron mobilisation; iron substrate. UK Article 13.1 B2 normal-metabolism-of-iron claim.
Evidence: UK Article 13.1 claim authorised. [5]
Doses studied: 1.4 mg B2 + 14 mg iron daily.