If you’ve been told your bloodwork is normal but you’re still exhausted, getting winded on the stairs, or noticing more hair in your brush, you’re not imagining it. Iron is one of the most common things I look at when someone comes to me feeling depleted, and it’s one of the places where “normal” on a lab report doesn’t always tell the whole story.
In Part 1 of my sleep series, I mentioned that iron deserves its own conversation. So, here it is.
Why your “normal” ferritin might not feel normal
Ferritin is the protein your body uses to store iron, and it’s the main blood test for checking your iron reserves.
Here’s something most people don’t know about lab ranges. A “normal” range is usually built by testing a large group of people and taking the middle 95% of their results. That works well when the group is healthy. But iron deficiency is very common, especially for women, and it often doesn’t cause obvious symptoms until it’s fairly advanced, so the people used to build ferritin ranges may include many who are already low. Researchers comparing these population-based ranges with the levels where the body actually starts showing signs of deficiency found that the population-based lower limits were too low [1].
The numbers bear this out. In a US national survey of girls and young women aged 12 to 21, nearly 4 in 10 had iron deficiency, but only about 6% had iron deficiency anemia [2]. Most were low in iron without being anemic, which is exactly the group a standard screen can miss.
This is why the guidelines recently changed. In 2026, the American Society of Hematology (ASH) released its first guideline for diagnosing iron deficiency, and it raised the ferritin thresholds many labs have traditionally used. For most adults, including women who menstruate, iron deficiency is now defined as a ferritin below 30 µg/L. For adults with symptoms or risk factors for iron deficiency, including heavy or irregular periods, the threshold rises to below 50 µg/L [3]. In other words, how you’re feeling counts: if you have symptoms, a ferritin in the 30s or 40s may be worth a closer look. (In Canada, ferritin is reported in µg/L, which is the same number as the ng/mL you may see in American sources.)
The guideline also sets thresholds for pregnancy, when iron needs rise to support both you and your baby. During pregnancy, iron deficiency is defined as a ferritin below 30 µg/L, or below 50 µg/L if anemia is also present [3]. If you’re pregnant or planning a pregnancy, checking iron early gives us time to build up your stores, and I’m happy to work alongside your midwife, obstetrician, or family doctor so your care stays coordinated.
Iron deficiency matters for more than how you feel day to day. In a German study of about 5,000 adults aged 35 to 74, followed for roughly 10 years, those with a ferritin below 30 µg/L had a higher risk of death from any cause, even after accounting for anemia and heart disease risk factors [4]. This kind of study shows a link (not cause), but it’s one more reason not to brush low iron off.
How iron works in your body
It helps to picture iron in three places:
Storage (ferritin): your iron savings account.
Transport (transferrin): the delivery trucks that carry iron through your blood to where it’s needed.
Use (hemoglobin): the oxygen-carrying protein inside your red blood cells. Each hemoglobin molecule needs iron to grab onto oxygen.
When iron runs low, these usually empty in order. First your stores drop (ferritin falls). Then less iron is available for transport. Only later does your body run short of iron to build hemoglobin, and that’s when anemia shows up. You can feel the effects well before that last step.
Anemia versus low iron without anemia
Iron deficiency anemia happens when there isn’t enough iron to build hemoglobin. Your body still makes red blood cells, but they come out smaller and paler than usual. Doctors call this microcytic (“small cell”) anemia. Because each cell carries less hemoglobin, each one carries less oxygen. Your heart and lungs have to work harder to deliver the same amount of oxygen to your muscles and brain, which is why even small efforts, like climbing stairs or carrying groceries, can leave you winded.
Iron deficiency without anemia is more subtle. Your hemoglobin may still look normal, but iron isn’t only used in blood. Your muscles and the energy-producing machinery inside your cells also depend on it. In a review of 22 trials in women of reproductive age, iron supplementation improved exercise capacity and lowered heart rate during a set workload [5]. In other words, the same effort took less work.
Symptoms of low iron, even without anemia
Low iron can show up in ways that are easy to blame on stress, busy seasons, or “just getting older”:
Fatigue. In a randomized trial of 198 menstruating women with unexplained fatigue, no anemia, and ferritin below 50 µg/L, fatigue scores dropped by about 48% with iron, compared with about 29% with placebo [6].
Brain fog and difficulty concentrating. If you’ve felt foggy, forgetful, or like your brain just isn’t as sharp as it used to be, you’re far from alone, and it can be frustrating to hear that your bloodwork is “fine.” The new ASH guideline lists symptoms like fatigue, reduced quality of life, and decreased cognitive function as reasons to look into iron [3]. That gives us one more reason to check iron, rather than writing these symptoms off.
Hair shedding. This one is debated. Some studies have linked lower iron stores with excessive hair loss in women who haven’t reached menopause [7], while other experts argue the evidence is still inconclusive [8]. It’s worth checking iron if you’re noticing more shedding, but low iron isn’t always the cause.
Restless legs. Restless legs syndrome is closely linked with iron, and sleep specialists recommend checking iron levels in anyone with significant symptoms [9]. It also connects back to sleep, which I discussed in my perimenopause sleep series.
Brain fog and difficulty concentrating. If you’ve felt foggy, forgetful, or like your brain just isn’t as sharp as it used to be, you’re far from alone, and it can be frustrating to hear that your bloodwork is “fine.” The new ASH guideline lists symptoms like fatigue, reduced quality of life, and decreased cognitive function as reasons to look into iron [3]. That gives us one more reason to check iron, rather than writing these symptoms off.
What ties these together is that symptoms can start when ferritin is low but hemoglobin is still normal. That’s why the new thresholds matter, especially the higher cutoff for people with symptoms: they’re designed to catch iron deficiency whether or not anemia has developed [3].
Ferritin needs context: the inflammation question
Ferritin has a quirk. It rises when there’s inflammation or infection in the body, so it can look normal, or even high, while your actual iron stores are low. The World Health Organization recommends checking inflammatory markers alongside ferritin where inflammation may be present [10]. The new ASH guideline also uses a higher ferritin threshold (below 100 µg/L) for adults with inflammatory conditions [3].
In practice, I like to look at ferritin together with inflammatory markers such as CRP and ESR, so that a ferritin that appears “normal” isn’t hiding a true deficiency.
Looking at the full iron picture
Ferritin is the starting point, but a few other markers help us to figure out what’s really going on:
Transferrin saturation tells us how full the delivery trucks are. When it’s low (below 20%), less iron is reaching your tissues. ASH uses it as an alternative way to diagnose iron deficiency in people with inflammatory conditions, such as inflammatory bowel disease, chronic kidney disease, heart failure, or rheumatologic conditions, where ferritin is harder to read. It’s best measured on a fasting blood sample [3].
TIBC (total iron-binding capacity) reflects how much transferrin you have. When iron runs low, the body often makes more transferrin to grab whatever iron it can, so TIBC tends to rise.
Serum iron shows how much iron is circulating at that moment. It changes a lot from day to day and with meals, so it’s most useful alongside the others.
A complete blood count (CBC) shows hemoglobin and red blood cell size, so we can tell whether anemia has developed.
Taken together, these markers help tell true iron deficiency apart from inflammation, and they help us to show how far along it is.
Where your gut fits in
Iron is absorbed in your digestive tract, so how your gut is working matters too. The new ASH guideline lists several situations where screening for iron deficiency makes sense, including digestive conditions like inflammatory bowel disease, celiac disease, H. pylori infection, and reflux (GERD), as well as use of acid-reducing medications (PPIs) and vegetarian or vegan eating [3]. In practice, I take it one step further and also consider checking iron in people with non-celiac gluten sensitivity. Some people with severe sensitivity need to manage it much like celiac disease, including avoiding cross-contamination, and when the gut is that reactive, it’s worth making sure iron absorption isn’t being affected as well. If you’ve read Test, Don’t Guess: Solving the Gut Puzzle, you’ll know how much the gut can affect the rest of the body, and in Hormones and the Gut: What’s the Connection?, I talked about how digestion can change during perimenopause. It’s one more example of why I look at the whole picture: low iron isn’t always about how much you’re eating. Sometimes it’s about how much you’re absorbing.
you guessed it: Test, don’t guess
Low iron is common, it’s often missed, and its symptoms overlap with thyroid issues, perimenopause, poor sleep, and stress. That’s why I don’t guess. I look at ferritin alongside a CBC, inflammatory markers, and, if indicated, iron studies. Then we put it all in the context of your symptoms, your periods, and your history. If you already have recent bloodwork, I’m happy to review it with you. Sometimes the answer is already there, sitting just inside the “normal” range.
If this sounds like you, I offer virtual care in Ontario and Manitoba. You can book an appointment through Jane, or send me a question through the contact form.
General information only, not medical advice.
References
Sezgin G, Monagle P, Loh TP, et al. Clinical thresholds for diagnosing iron deficiency: comparison of functional assessment of serum ferritin to population based centiles. Sci Rep. 2020;10:18233. doi:10.1038/s41598-020-75435-5
Weyand AC, Chaitoff A, Freed GL, et al. Prevalence of iron deficiency and iron-deficiency anemia in US females aged 12-21 years, 2003-2020. JAMA. 2023;329(24):2191-3. doi:10.1001/jama.2023.8020
Powers JM, Lim MY, Achebe MO, et al. American Society of Hematology 2026 guidelines for diagnosis of iron deficiency. Blood Adv. 2026;10(21):7353-74. doi:10.1182/bloodadvances.2025015950
Schrage B, Rübsamen N, Schulz A, et al. Iron deficiency is a common disorder in general population and independently predicts all-cause mortality: results from the Gutenberg Health Study. Clin Res Cardiol. 2020;109(11):1352-7. doi:10.1007/s00392-020-01631-y
Pasricha SR, Low M, Thompson J, Farrell A, De-Regil LM. Iron supplementation benefits physical performance in women of reproductive age: a systematic review and meta-analysis. J Nutr. 2014;144(6):906-14.
Vaucher P, Druais PL, Waldvogel S, Favrat B. Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin: a randomized controlled trial. CMAJ. 2012;184(11):1247-54. doi:10.1503/cmaj.110950
Deloche C, Bastien P, Chadoutaud S, et al. Low iron stores: a risk factor for excessive hair loss in non-menopausal women. Eur J Dermatol. 2007;17(6):507-12. doi:10.1684/ejd.2007.0265
Olsen EA. Iron deficiency and hair loss: the jury is still out. J Am Acad Dermatol. 2006;54(5):903-6. doi:10.1016/j.jaad.2005.10.038
Winkelman JW, Berkowski JA, DelRosso LM, et al. Treatment of restless legs syndrome and periodic limb movement disorder: an American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med. 2025;21(1):137-52. doi:10.5664/jcsm.11390
World Health Organization. WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations. Geneva: WHO; 2020.