Picture a woman who sees her GP because she's exhausted and losing hair. Her ferritin comes back at 22 ug/L. The lab slip says "normal (15 to 200)", and she is told it's fine.
If you have searched "ferritin normal but tired", you are not imagining your symptoms. A ferritin of 22 is read against the laboratory's own range, and a 2024 systematic review found that the lower limits of those ranges for women usually sit well below the 30 ug/L that Australian guidance uses to diagnose iron deficiency (Truong et al., Lancet Haematology 2024).
Ferritin, the storage protein
Ferritin is the protein that stores iron inside your cells. Think of it as your iron savings account. When the body needs iron, to build red blood cells, fuel mitochondrial energy production, synthesise neurotransmitters, it draws on ferritin stores first.
When your serum ferritin is measured, you're getting a snapshot of how full that savings account is. Low serum ferritin is, in almost all cases, a reliable indicator of depleted iron stores. It drops before haemoglobin, transferrin saturation, or any other standard biomarker of iron status.
Ferritin reference ranges for women
Lab reference ranges are built by sampling a large population, measuring their ferritin, and calling "normal" the middle 95% of that sample. A 2024 systematic review of where ferritin reference intervals come from found that about half of the underlying studies did not explicitly screen out people at risk of iron deficiency, and that the lower limits reported for women sit well below 30 ug/L (Truong et al., Lancet Haematology 2024).
If the sample includes women who are already iron deficient, the bottom of the range is pulled down with them.
Heavy menstrual bleeding is the most common cause of iron deficiency in apparently healthy women (Dugan et al., Anaesthesia 2021).
Australian guidance treats a serum ferritin below 30 ug/L as iron deficiency (Balendran and Forsyth, Australian Prescriber 2021;44(6):193-6). At that threshold the test has high sensitivity and specificity for absent iron stores. The WHO's own threshold for apparently healthy adults is lower, below 15 ug/L, and recent research suggests the WHO threshold underestimates how common iron deficiency is (Addo et al., Lancet Global Health 2025).
Three scenarios of hidden deficiency
Scenario 1. Ferritin between 15 and 30, symptomatic
Your lab may flag this as normal, because laboratory lower limits for ferritin usually sit below 30 (Truong et al., Lancet Haematology 2024). Australian guidance treats a ferritin below 30 ug/L as iron deficiency (Balendran and Forsyth, Australian Prescriber 2021;44(6):193-6). If you have symptoms, that is a reason to discuss treatment with your GP, who should also look for the cause.
Scenario 2. Ferritin between 30 and 50, symptomatic
This result sits above the Australian threshold for iron deficiency, so iron is one possible cause among several. Even below 30, Australian guidance describes the evidence that iron relieves symptoms in people without anaemia as limited and variable (Balendran and Forsyth, Australian Prescriber 2021;44(6):193-6). Above 30, this is a conversation with your GP about other causes as well as iron.
Scenario 3. Normal ferritin with a raised C-reactive protein (CRP)
Ferritin is an acute phase reactant. It rises in response to inflammation, infection, autoimmune activity, and obesity. If your CRP or ESR is elevated, your ferritin is artificially inflated. Australian guidance handles this with a higher threshold: in inflammatory states, a ferritin below 100 ug/L with a transferrin saturation below 20% can be used to diagnose iron deficiency (Balendran and Forsyth, Australian Prescriber 2021;44(6):193-6).
The full iron panel
A haemoglobin on its own is the cheapest possible look. A full iron assessment covers these markers, listed in the order in which they deteriorate:
| Biomarker | What it tells you | Red flag threshold (women) |
|---|---|---|
| Ferritin | Iron stores (the savings account) | < 30 ug/L (< 100 ug/L with inflammation) |
| Transferrin saturation | How effectively the body is moving iron | < 20% |
| MCV | Size of red blood cells (shrinks in deficiency) | < 80 fL |
| Haemoglobin | Oxygen-carrying capacity of blood | < 120 g/L (adult women) |
| CRP (context) | Inflammation, tells you if ferritin is artificially elevated | > 5 mg/L flags inflammation |
Haemoglobin is the last marker to drop, so by the time your Hb flags as low, iron deficiency has already reached its most advanced stage. Relying on haemoglobin alone is like checking your smoke alarm after the house has already burned down.
A script for your general practitioner (GP)
Most general practitioners (GPs) work from reference ranges supplied by the lab and a 10-minute appointment slot. You can improve your odds of a proper workup by walking in with a specific ask.
"I'd like a full iron panel please: ferritin, transferrin saturation, MCV, haemoglobin, and CRP. I've read that Australian guidance treats a ferritin under 30 as iron deficiency, and I'd like my result interpreted against that threshold as well as the laboratory range. I have [list your symptoms], and if my ferritin is under 30, I'd like to discuss treatment and what might be causing it."
Naming the biomarkers and the threshold pre-empts the "but your labs are normal" reply.
Second opinions
If your GP refuses to order a full panel, refuses to interpret against modern thresholds, or insists that your ferritin of 22 is fine despite textbook symptoms, it is reasonable to seek a second opinion. Options include:
- A women's health GP or practitioner who sees iron deficiency regularly
- A haematologist, especially if you have heavy menstrual bleeding, malabsorption, or prior pregnancy complications
Summary
"Normal" on a lab slip describes the middle 95% of a sampled population. If your ferritin is under 30 and you have symptoms, Australian guidance treats that as iron deficiency, and a result between 30 and 50 is still worth discussing with your general practitioner (GP).
This article is educational and not medical advice. Always discuss significant changes to supplementation or testing with a qualified clinician who knows your full history.
Related articles
- Iron deficiency without anemia (IDNA)
- Iron Deficiency Body Map
- A Practical Guide to Iron Deficiency and Anaemia
Sources
The papers behind each citation on this page.
- Addo OY, Mei Z, Jefferds MED, et al. Physiologically based serum ferritin thresholds for iron deficiency among women and children from Africa, Asia, Europe, and central America: a multinational comparative study. The Lancet Global Health 2025;13(5):e831-e842. doi:10.1016/S2214-109X(25)00009-9
- Balendran S, Forsyth C. Non-anaemic iron deficiency. Australian Prescriber 2021;44(6):193-196. doi:10.18773/austprescr.2021.052
- Dugan C, MacLean B, Cabolis K, et al. The misogyny of iron deficiency. Anaesthesia 2021;76(Suppl 4):56-62. doi:10.1111/anae.15432
- Truong J, Naveed K, Beriault D, et al. The origin of ferritin reference intervals: a systematic review. The Lancet Haematology 2024;11(7):e530-e539. doi:10.1016/S2352-3026(24)00103-0