By Kirstie Vesseur, Registered Clinical Nutritionist (CNA), Legacy Nutrition, NZ and Australia.
You got your blood results back and the note said your ferritin was "a bit low", or "fine, nothing to worry about". Meanwhile you are exhausted by 2pm, cold when everyone else is comfortable, and finding more hair in the shower than you would like.
I see low ferritin in clinic almost every week. It is one of the most common findings in women, and one of the most worth getting to the bottom of. Here is why it happens, what your results may not be telling you, and what to eat and take.
What low ferritin tells you
Ferritin is a protein that stores iron. A ferritin blood test is the most useful single marker of how much iron you have in reserve.
Ferritin usually falls before haemoglobin does, so you can have low iron stores without being anaemic. This stage, iron deficiency without anaemia, is common in women who have periods. Symptoms that have been linked with low iron stores include:
tiredness and low stamina
poor concentration
hair shedding
restless legs
breathlessness on stairs or during exercise
low mood or irritability
feeling cold
None of these is specific to iron, so a blood test is the only way to know. The good news: a systematic review of randomised trials found that iron reduced self-reported fatigue in iron-deficient adults who were not anaemic (fatigue was measured in four of the trials), although it did not improve measured physical performance.
Why is my ferritin low?
Heavy or long periods
This is the most common cause I see in women who still have periods. Many women have had heavy periods for so long they assume it is normal. Signs your periods may be heavy include:
changing a pad or tampon every hour, or getting up at night to change it
passing clots larger than a 50 cent coin
bleeding through to your clothes
bleeding for more than 8 days
If this sounds like you, please talk to your GP. Fibroids, endometriosis and adenomyosis can all play a part, and my post on the adenomyosis diet covers that side.
Not enough iron in your food
Women aged 19 to 50 need about 18 mg of iron a day, rising to 27 mg in pregnancy and dropping to 8 mg after menopause. There are two types of dietary iron:
Haem iron from red meat, fish and poultry, which the body absorbs relatively well.
Non-haem iron from legumes, tofu, seeds, leafy greens and fortified cereals, which is absorbed less efficiently.
Women who eat little or no red meat can maintain healthy iron, but it takes more planning.
Poor absorption
You can eat well and still struggle to absorb iron. Common reasons include:
coeliac disease, which is worth ruling out if iron stays low (ask your GP for a coeliac blood test before cutting out gluten)
inflammatory bowel disease
low stomach acid, for example from long-term acid-reducing medication or atrophic gastritis
tea, coffee and calcium taken with iron-rich meals
Pregnancy and postpartum
Pregnancy uses a lot of iron, and birth can add blood loss on top. Many mums move into the postpartum period with depleted stores, and fatigue gets put down to the baby when iron may also be part of it. My post on postpartum fatigue and blood tests goes further.
Exercise
Regular training, especially endurance running, can increase iron losses through sweat, the gut and the breakdown of red blood cells. Active women may need their ferritin checked more often.
What a standard result may not show
The cut-offs are being revised
UK gastroenterology guidelines describe a ferritin below 15 µg/L as absent iron stores and below 30 µg/L as generally low. In 2026 the American Society of Hematology recommended a cut-off of 30 µg/L for adults, and up to 50 µg/L for people with symptoms, heavy menstrual bleeding or other risk factors. Some lab reference ranges start lower than this, so a result inside the printed range can still point to low stores. The New Zealand Optimal Ranges Guide sets out the ranges I work with and why.
Ferritin can be falsely reassuring
Ferritin rises with inflammation or infection, so a ferritin that looks fine can hide low iron if you are unwell or have ongoing inflammation. The World Health Organization suggests a higher cut-off (below 70 µg/L) in adults with infection or inflammation. Inflammation also raises a hormone called hepcidin, which reduces iron absorption. This is why a full iron study is more useful than ferritin alone:
ferritin
serum iron
transferrin saturation
full blood count, including haemoglobin
CRP (an inflammation marker)
Finding the cause matters
Taking iron without asking why ferritin dropped can mean levels fall again once you stop. Working out whether it is bleeding, intake, absorption or a mix of these is what keeps levels up. If you are post-menopausal, or iron deficiency is unexplained, your GP may need to investigate further, because it can be a sign of a gut problem.
How nutrition can help
Iron-rich foods
Haem sources: beef (around 3 mg per 100 g), lamb (around 2.5 mg per 100 g), venison, sardines and mussels. Two to three red meat meals a week, around 100 g cooked each, is a practical target for many women.
Plant sources: tofu (about 3 mg per 100 g), cooked lentils, chickpeas and kidney beans (roughly 3 mg per 100 g), pumpkin seeds, leafy greens and iron-fortified cereals (check the label).
Boost absorption
Pair plant iron with vitamin C foods: kiwifruit, capsicum, citrus, tomato or broccoli.
Keep tea and coffee at least an hour away from iron-rich meals and supplements.
Have dairy and calcium supplements at a different meal from your main iron source.
Supplements
Please test before taking iron. Too much iron is harmful, and some people have haemochromatosis, an inherited condition where the body stores too much iron. About 1 in 200 people of northern European descent are genetically at risk.
Prescribed iron: if your GP confirms iron deficiency, they may prescribe a funded tablet. In New Zealand this is now ferrous fumarate (Ferro-tab, 65.7 mg elemental iron per tablet), after supply of Ferrograd ran out in 2025. UK guidelines suggest 50 to 100 mg of elemental iron once a day as a starting point.
Every second day: studies in iron-deficient women show iron is absorbed better when taken on alternate days rather than on consecutive days, so your GP may suggest this, especially if daily iron upsets your stomach.
Iron bisglycinate: a meta-analysis of randomised trials, mostly in pregnant women, found ferrous bisglycinate caused fewer gut side effects than other iron forms. In New Zealand, iron supplements sold outside pharmacies provide no more than 24 mg of elemental iron a day. Check the label for elemental iron, not the weight of the compound.
Stay under the upper limit: do not take more than 45 mg of elemental iron a day (the adult upper level of intake in New Zealand and Australia) unless your GP has prescribed a treatment dose and is monitoring your bloods.
Check with your GP or pharmacist if you take medication, are pregnant or breastfeeding, as iron can interact with some medicines. Keep iron supplements out of reach of children.
Recheck
If you are anaemic, your GP will usually recheck haemoglobin within about four weeks. Guidelines suggest continuing iron for around three months after haemoglobin returns to normal, to rebuild stores, so ferritin is often rechecked at around three months.
Frequently asked questions
Can my ferritin be normal and still cause symptoms?
It can. A result inside the lab range is not always where you feel your best, and ferritin can look higher than your true iron status if inflammation is present. Looking at the full iron study alongside your symptoms gives a better picture.
Should I take iron with food?
Iron is absorbed best on an empty stomach or between meals, but many women find it upsets their stomach that way. Taking it with a small meal, or on alternate days, are common compromises. Your GP or pharmacist can help you find what works.
For a deeper look at iron, see my article Could Low Iron Be the Reason You're So Tired?
Where to start
If you have been told your ferritin is low, or "fine" while you still feel awful, it is worth understanding why.
Want help with this one-on-one? See how I work with women on women’s hormone support, or browse all my services.
This article is general education, not personal medical advice. Please talk with your GP before starting supplements or changing medication.
References
Powers JM, et al. American Society of Hematology 2026 guidelines for diagnosis of iron deficiency. Blood Advances, 2026. https://doi.org/10.1182/bloodadvances.2025015950
Snook J, et al. British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults. Gut, 2021. https://pubmed.ncbi.nlm.nih.gov/34497146/
Houston BL, et al. Efficacy of iron supplementation on fatigue and physical capacity in non-anaemic iron-deficient adults: a systematic review of randomised controlled trials. BMJ Open, 2018. https://bmjopen.bmj.com/content/8/4/e019240
Stoffel NU, et al. Iron absorption from supplements is greater with alternate day than with consecutive day dosing in iron-deficient anemic women. Haematologica, 2020. https://haematologica.org/article/view/9379
Fischer JAJ, et al. 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. https://pubmed.ncbi.nlm.nih.gov/36728680/
World Health Organization. WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations. 2020. https://www.who.int/tools/elena/interventions/ferritin-concentrations
Healthify He Puna Waiora. Heavy periods. https://healthify.nz/health-a-z/p/periods-heavy-bleeding
Pharmac. Ferrous sulfate (Ferrograd) iron tablets: discontinued. 2025. https://www.pharmac.govt.nz/medicine-funding-and-supply/medicine-notices/ferrograd
