Iron

Iron is the mineral your body uses to carry oxygen. It sits at the centre of haemoglobin in your red blood cells and inside myoglobin in your muscles. It also powers the energy reactions happening in every cell.^[1] Women lose iron with every period. Over years this is the single biggest reason iron stores run low.

If you have been told to take iron because your ferritin is low, because you are tired or anaemic, because you are planning a pregnancy or because your periods are heavy, this page covers which form is gentlest, how much you need and what the research shows.

Forms of iron

Iron is used in supplements in several chemical forms. They differ meaningfully in how well your body absorbs them and in how hard they are on the gut.

Ferrous sulfate is the cheapest and most common form. It is well absorbed but reliably causes nausea, constipation and abdominal pain in a meaningful share of women, which is the main reason people abandon iron supplementation.^[1]

Ferrous fumarate and ferrous gluconate are also iron salts. Similar absorption profile to sulfate with slightly different tolerance.

Iron bisglycinate is iron bound to two molecules of the amino acid glycine. A 2023 systematic review and meta-analysis in Nutrition Reviews found that pregnant women supplemented with bisglycinate reached higher haemoglobin and reported significantly fewer gastrointestinal side effects than women on iron salts, despite using lower elemental iron doses.^[5]

Heme iron is the form found in red meat, fish and poultry. It is absorbed more efficiently than non-heme iron from plants and is not affected by phytates, polyphenols or calcium in the meal.^[1]

Vitamin C taken alongside non-heme iron significantly increases its absorption. This is the rationale for the iron and vitamin C pairing in nōuxx Bloody Berry.^[1]

How much you need

The European Food Safety Authority recommends 16 mg of iron per day for menstruating women. Pregnancy raises that need to 27 mg.^[1]

Around one in three women of reproductive age worldwide has iron deficiency or iron deficiency anaemia. Heavy menstrual bleeding is the main driver in adolescent girls and adult women. It is consistently under-recognised both by women themselves and by clinicians.^[3] Calcium, coffee and tea taken with an iron meal lower iron absorption. Vitamin C raises it.^[1]

The science on women's health

Period loss and energy

Iron deficiency in women of reproductive age is one of the most common nutritional deficiencies in the world. Consequences extend well beyond anaemia. Chronic fatigue, low mood and cognitive impairment all show up at the iron-deficient stage, before haemoglobin falls.^[4]

A 2022 systematic review and meta-analysis pooled iron supplementation trials in postpartum women. Iron significantly reduced fatigue scores. In the same review, women who were iron-deficient or anaemic were 1.66 times more likely to experience symptoms of depression than iron-replete women.^[7]

A 2026 randomised controlled trial in 164 non-anaemic but iron-deficient women of reproductive age confirmed that iron therapy alleviated fatigue and raised ferritin. This is the group most often missed in standard practice. Haemoglobin can sit in the normal range while ferritin and energy do not.^[6]

Cognition and focus

A 2023 review in the American Journal of Obstetrics and Gynecology drew together the evidence linking heavy menstrual bleeding, iron deficiency and cognitive function in girls and women. The authors flagged effects on focus, work and school performance. They called out the routine normalisation of heavy periods as a public health gap.^[3]

The biology fits. Iron is needed for the dopamine, serotonin and noradrenaline pathways that drive attention and motivation. When iron stores run low, those pathways slow down before haemoglobin falls.^[1]

EU authorised health claims

Under EU law, iron is officially authorised to carry the following health claims:

• Iron contributes to the reduction of tiredness and fatigue
• Iron contributes to normal energy-yielding metabolism
• Iron contributes to normal formation of red blood cells and haemoglobin
• Iron contributes to normal oxygen transport in the body
• Iron contributes to the normal function of the immune system
• Iron contributes to normal cognitive function
• Iron contributes to normal cognitive development of children
• Iron has a role in the process of cell division^[2]

References

[1] National Institutes of Health, Office of Dietary Supplements. Iron: Fact Sheet for Health Professionals. ods.od.nih.gov/factsheets/Iron-HealthProfessional

[2] Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. Official Journal of the European Union, 25 May 2012. eur-lex.europa.eu

[3] Munro MG, Mast AE, Powers JM, et al. The relationship between heavy menstrual bleeding, iron deficiency, and iron deficiency anemia. American Journal of Obstetrics and Gynecology 2023;229(1):1-9. doi.org/10.1016/j.ajog.2023.01.017

[4] Tang GH, Sholzberg M. Iron deficiency anemia among women: an issue of health equity. Blood Reviews 2024;64:101159. doi.org/10.1016/j.blre.2023.101159

[5] Fischer JAJ, Cherian AM, Bone JN, Karakochuk CD. The effects of oral ferrous bisglycinate supplementation on hemoglobin and ferritin concentrations in adults and children: a systematic review and meta-analysis of randomized controlled trials. Nutrition Reviews 2023;81(8):904-920. doi.org/10.1093/nutrit/nuac106

[6] Sultana N, Bajwa FA, Sikandar MZ, et al. Effect of iron therapy on fatigue symptoms in non-anaemic iron deficient women of reproductive age: a randomized controlled trial. Journal of the Pakistan Medical Association 2026;76(1):4-7. doi.org/10.47391/JPMA.22068

[7] Moya E, Phiri N, Choko AT, Mwangi MN, Phiri KS. Effect of postpartum anaemia on maternal health-related quality of life: a systematic review and meta-analysis. BMC Public Health 2022;22:364. doi.org/10.1186/s12889-022-12710-2