Teen girls, women, tired all the time? Low iron could be the missing piece

Nutritionist based in Ireland with ONLINE support and in-person appointments in Adare, Newcastle West, Limerick, Abbeyfeale, Charleville, Kanturk, Midleton, Youghal, Cork, Dublin and Dungarven.

Summary:
You might notice a teenager who feels wiped out, foggy, anxious, breathless walking up stairs, or shedding more hair than usual. That cluster of symptoms is often blamed on “hormones” or exam stress. A new Swedish study puts iron deficiency firmly back on the radar: 38% of 475 teenage girls tested were iron deficient, rising to 69% in vegetarians and vegans, 49% in pescatarians, and still 31% in omnivores. Anaemia was uncommon, so ferritin testing matters. Screening and simple changes can turn energy, mood and focus around. (PMC)

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Why iron matters so much in the teenage years

Iron helps your body carry oxygen, make energy, and build neurotransmitters that support focus and mood. Teenage girls have higher needs because of growth and the start of menstruation. In the UK and Ireland, the daily reference intake for girls and women who menstruate is 14.8 mg. Plant-based eaters often need more because non-haem iron is harder to absorb; a common rule of thumb is ~1.8× higher, which would mean about 26–27 mg for a vegetarian or vegan teen. Adults who menstruate also average 14.8 mg, though some countries set 18 mg. These are population guidelines, not prescriptions for every individual. (British Dietetic Association)

Here is the headline finding that deserves attention: among Swedish teens, iron deficiency hit 38% overall, 69% in vegetarians/vegans, 49% in pescatarians, and 31% in omnivores. Anaemia affected only 3%. That means many girls feel the effects long before a standard haemoglobin test flags a problem. (PMC)

A quick mechanism in plain English: Ferritin is your iron-storage protein. Hepcidin is a hormone that turns iron absorption up or down. Inflammation, frequent dosing of iron, and some gut conditions can raise hepcidin, reducing absorption. That is one reason why alternate-day iron dosing sometimes works better than daily. (PMC)

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Signs to look for

• Constant fatigue, “wired but tired” evenings, unrefreshing sleep.

• Pale inner eyelids, easy breathlessness, frequent sighing.

• Brain fog, poor concentration, low motivation.

• Anxious or low mood, particularly around periods.

• Heavy periods, or in severe deficiency, missed periods.

• Hair shedding or widening part lines.

• Cold hands and feet. (PMC)

Mood deserves a note. Iron status links to brain iron and neurotransmitters. Recent adolescent data associate low iron with more internalising symptoms, and brain imaging studies show iron deficiency without anaemia can relate to lower striatal iron and altered brain structure and function. Not all anxiety or depression is iron-related, but it is sensible to check. (PMC)

Hair loss can be multifactorial. Some dermatology papers associate low ferritin with non-scarring hair shedding, while others find no strong link. If hair is thinning and energy is low, ask the GP for ferritin alongside other checks. (PMC)

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Why food alone may not be enough for some teens

Many girls experiment with diet, eat small portions, or avoid red meat. Wholegrains and legumes are brilliant nutritionally, yet their phytic acid can inhibit iron absorption. The Swedish study found lower red-meat intake and higher vegetarian patty and legume intake were linked with deficiency, even though anaemia was rare. Add heavy periods and busy schedules, and it is easy to fall short. (PMC)

Helpful food ideas: pair plant-iron with vitamin C (berries, citrus, peppers), try leavened sourdough, soak or sprout pulses to reduce phytate, and include fish or poultry if acceptable. If coeliac disease, IBD, reflux medication, or Helicobacter pylori are in the picture, absorption can be reduced, so medical input is essential. (NICE)

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What to ask the GP to test

• Serum ferritin (the single most useful test). Ferritin <15 µg/L is diagnostic of iron deficiency in most teens. In inflammation, use a higher threshold.
• Full blood count and transferrin saturation to clarify the picture.
• C-reactive protein to check for inflammation.
• If periods are heavy, follow NICE HMB guidance, and consider thyroid, bleeding disorders, or coeliac testing where appropriate. (Wiley Online Library)

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What you can try over the next fortnight

1. Book bloods and track symptoms. Keep a short log of fatigue, breathlessness, mood and hair shedding. If periods are heavy, note pad or tampon changes and clots. NICE NG88 has clear criteria for assessment. (NICE)
2. Optimise meals for iron. Include an iron-rich food twice daily. For plant-based teens, add a vitamin-C fruit or veg to each main meal. Leave a two-hour gap between iron-rich meals or supplements and calcium, tea or coffee. (Office of Dietary Supplements)
3. Consider a gentle iron supplement if ferritin is low or borderline and the GP agrees. Evidence suggests single-dose alternate-day iron may improve absorption and reduce tummy upset compared with daily dosing. Typical elemental iron targets for adolescents are in the 40–100 mg range, adjusted clinically. Check labels, start low, and build. (PubMed)
4. Support the gut. If there is IBS, reflux, coeliac disease, IBD or suspected H. pylori, get these addressed because they alter absorption. Treating the cause prevents the iron “yo-yo.” (NICE)
5. Tackle heavy periods. Tranexamic acid or certain contraceptive options can reduce blood loss, if clinically appropriate. Follow guideline-led care. (NICE)

Safety note: Always speak with your GP or pharmacist before starting supplements, especially if on medication. Stop iron and seek advice if you have severe stomach pain, black stools that worry you, or allergic reactions.

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A note for parents and carers

As you know teens value what feels immediately relevant. Framing iron as support for clear thinking, steady energy for sport, and stronger, shinier hair can make sense to them. In clinic, many young women engage once they see their ferritin results and a simple plan. You can help by offering iron-friendly snacks, spacing dairy away from iron, and celebrating small wins.

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Iron and menstruation go both ways

Low iron can increase menstrual bleeding for some, and heavier periods then push iron lower. If periods are prolonged, flood through protection, or cause dizziness, follow NICE NG88 for assessment and management. Anaemia is not required for meaningful symptoms or for treatment to be justified. (NICE)

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FAQs

1) What ferritin level is “low” for a teen?
Many guidelines use ferritin <15 µg/L as diagnostic for deficiency when inflammation is absent. A level under ~30 µg/L often prompts treatment consideration if symptoms fit, and higher cut-offs are used when inflammation is present. Your clinician will interpret this in context. (PMC)

2) Do vegetarians and vegans always need supplements?
Not always. Well-planned plant-based diets can work, but non-haem iron is harder to absorb, so the NIH suggests ~1.8× the usual intake. Real-world screening, like the Swedish study, shows higher rates of deficiency in plant-based teens, so testing and targeted advice help. (Office of Dietary Supplements)

3) Is alternate-day iron really better?
Several studies show alternate-day dosing increases absorption compared with consecutive daily dosing, likely by lowering hepcidin’s “block.” It also suits sensitive stomachs. Your GP can advise on dose and product. (PubMed)

4) Could low iron explain anxiety or brain fog?
It can contribute. Observational studies link iron deficiency to more internalising symptoms in adolescents, and imaging work shows lower brain iron in iron-deficient teens without anaemia. These are associations, not proof for every person, but worth checking. (PMC)

5) What about hair loss?
Some studies associate low ferritin with increased shedding, while others do not. If shedding is new or distressing, ask for ferritin and thyroid checks, then address the basics while the cause is clarified. (PMC)

6) When should we look for an underlying cause?
If iron keeps dropping, periods are very heavy, or there are gut symptoms, check for coeliac disease, IBD, reflux medicines that reduce acid, or H. pylori. Treating the cause helps iron stay up. (NICE)

7) What if tablets are not tolerated or iron stays low?
Different oral forms exist, and dosing can be adjusted. If absorption is poor or losses are high, clinicians may consider intravenous iron. This is a medical decision based on guidelines. (gut.bmj.com)

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Educational disclaimer

This article/resource is for education, not a substitute for medical care. Always consult your GP or pharmacist before changing medication or supplements, and seek urgent care for severe symptoms.

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References

1. Stubbendorff A, et al. Iron insight: exploring dietary patterns and iron deficiency among teenage girls in Sweden. Eur J Nutr. 2025. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11880139/
2. British Dietetic Association. Iron — requirements. https://www.bda.uk.com/resource/iron-rich-foods-iron-deficiency.html
3. NHS. Iron: vitamins and minerals. https://www.nhs.uk/conditions/vitamins-and-minerals/iron/
4. NIH Office of Dietary Supplements. Iron Fact Sheet. https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/
5. NIH ODS Consumer: vegetarians need ~1.8× iron. https://ods.od.nih.gov/factsheets/Iron-Consumer/
6. Hands K, et al. British Society for Haematology guideline update on iron deficiency. https://onlinelibrary.wiley.com/doi/10.1111/bjh.19440
7. NICE NG88. Heavy menstrual bleeding: assessment and management. https://www.nice.org.uk/guidance/ng88
8. Nemeth E, Ganz T. Hepcidin and iron in health and disease. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9943683/
9. Annual Review of Medicine. Hepcidin overview. https://www.annualreviews.org/doi/10.1146/annurev-med-043021-032816
10. Stoffel NU, et al. Alternate-day dosing increases iron absorption. https://pubmed.ncbi.nlm.nih.gov/29032957/
11. Stoffel NU, et al. Iron absorption higher with alternate day in IDA. https://www.haematologica.org/article/view/9379
12. von Siebenthal HK, et al. Alternate vs consecutive day oral iron. https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(23)00463-7/fulltext
13. Pantopoulos K, et al. Oral iron supplementation, new insights. https://haematologica.org/article/view/haematol.2024.284967
14. Iolascon A, et al. Recommendations for diagnosis and prevention of iron deficiency (WHO thresholds). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11247274/
15. RUH Bath. Ferritin interpretation for GPs. https://www.ruh.nhs.uk/pathology/documents/clinical_guidelines/HAEM_Ferritin_a_guide_for_GPs.pdf
16. ACOG Committee Opinion: Adolescents with heavy menstrual bleeding. https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2019/09/screening-and-management-of-bleeding-disorders-in-adolescents-with-heavy-menstrual-bleeding
17. Yaşa C, et al. Approach to abnormal uterine bleeding in adolescents. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7053441/
18. Chen MH, et al. Iron deficiency and psychiatric disorders (children and adolescents). https://bmcpsychiatry.biomedcentral.com/articles/10.1186/1471-244X-13-161
19. Fiani D, et al. Iron deficiency and internalising symptoms in adolescents. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11547248/
20. Fiani D, et al. ID without anaemia and adolescent brain iron. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2835510
21. Treister-Goltzman Y, et al. Iron deficiency and non-scarring alopecia review. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8928181/
22. Coeliac disease (NICE NG20 recommendations). https://www.nice.org.uk/guidance/ng20/chapter/recommendations
23. Kato S, et al. H. pylori-associated iron deficiency anaemia. https://www.mdpi.com/2077-0383/11/24/7351
24. British Society of Gastroenterology guideline on IDA treatment response. https://gut.bmj.com/content/70/11/2030

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When you are ready, we can tailor a simple, teen-friendly action plan with food, supplements if needed, and steady support for periods, mood and sleep.

CONTACT TO DISCUSS HOW WE CAN HELP

Contact Claire Russell Registered Nutritionist, Counsellor, Clinical Medical Hypnotherapist, Advanced RTT, Psychotherapy to discuss how we can help you or your young person quickly back to feeling well and happy.

Ring or text Claire 087 616 6638