Iron Deficiency: Signs, Testing & Who's at Risk (2026)
The honest picture: Most people are fine. Overall, iron deficiency is genuinely uncommon in US adults. But it isn't evenly spread — menstruating women, pregnant women, vegetarians and vegans, endurance athletes, frequent blood donors, people with heavy periods or GI blood loss, and long-term users of acid-reducing medication all carry real, elevated risk. If none of that applies to you and you feel fine, this isn't something to worry about.
The trap to know about: You can be iron deficient without being anemic. Ferritin, your iron storage level, can drop low enough to cause fatigue before hemoglobin falls into the anemia range (PMID: 12763985). A normal complete blood count doesn't rule out low iron as a cause of tiredness.
The testing nuance: A ferritin result flagged "normal" by the lab can still be too low. Labs typically flag deficiency under 12 ng/mL, but many clinicians treat anything under 30 ng/mL as functionally low in someone with symptoms (PMID: 39110847).
Symptoms of Iron Deficiency
Iron deficiency develops gradually, as your stores (ferritin) drain before your blood count actually falls. That means early symptoms are easy to write off as stress or poor sleep — which is exactly why testing beats symptom-matching:
Common Symptoms
- Fatigue and low energy — usually the first thing people notice, and the most common reason low iron gets tested for in the first place.
- Pale skin — from reduced red blood cell production, most visible in the face and inner eyelids.
- Cold hands and feet — reduced oxygen delivery to the extremities.
- Brittle or spoon-shaped nails — nails that crack, peel, or in more advanced cases curve upward (koilonychia).
- Hair shedding — more hair than usual coming out in the shower or brush.
- Restless legs — an urge to move the legs, especially at night. Low iron is a well-documented trigger, and iron therapy is a standard treatment for iron-related restless legs syndrome (PMID: 42371291).
- Craving ice or non-food items (pica) — an unusual but fairly specific sign of low iron. Craving and chewing ice specifically is called pagophagia.
- Shortness of breath on exertion — feeling winded doing things that used to be easy.
- Poor concentration and headaches — brain fog and a harder time focusing.
- Anemia, in more severe cases — once iron stores are exhausted, red blood cell production falls and hemoglobin drops.
The signature point worth knowing: you don't need anemia to feel the effects of low iron. Ferritin can fall low enough to cause real fatigue while hemoglobin still reads normal. A randomized, placebo-controlled trial gave iron to non-anemic women with unexplained fatigue and found the iron group's fatigue improved significantly more than the placebo group's (PMID: 12763985). In practice, this means "my bloodwork looks fine" doesn't fully rule out iron as a cause of tiredness — the ferritin number specifically is the one to check.
Low iron and low B12 also tend to cluster in the same people — vegetarians and vegans, and anyone with heavy periods or an absorption problem — so if you're getting one checked, it's worth checking the other too. See our B12 deficiency signs guide.
Who's Most at Risk?
| Risk Factor | Why It Matters |
|---|---|
| Menstruating women, especially heavy periods | Regular blood loss is the single biggest driver of iron deficiency in adults. NHANES data show women's deficiency rate running roughly ten times higher than men's, and nearly a quarter of women have low-normal iron stores. Heavier or longer periods mean more iron lost each cycle. See our iron for women guide. |
| Pregnancy | Blood volume expands and the growing fetus draws on maternal iron stores, so requirements rise sharply during pregnancy — often beyond what diet alone supplies. |
| Vegetarians and vegans | Plant-based (non-heme) iron is absorbed less efficiently than the heme iron in meat, fish, and poultry. It's not that plant-based diets can't supply enough iron, but the margin for error is smaller. |
| Endurance athletes | Distance runners and other endurance athletes lose iron through sweat, foot-strike red blood cell breakdown, and minor gut bleeding from prolonged exertion — a pattern sometimes called "sports anemia." |
| Frequent blood donors | Each whole-blood donation removes a meaningful amount of iron, and stores can take months to rebuild. Donating more often than your body can replenish is a common, overlooked cause of low ferritin. |
| Heavy periods or GI blood loss | Any source of chronic, ongoing blood loss — heavy menstrual bleeding, ulcers, hemorrhoids, or other gastrointestinal bleeding — drains iron faster than typical diet replaces it. Unexplained iron deficiency in someone who isn't menstruating is worth a doctor's evaluation to find the source. |
| Long-term acid-reducer (PPI) users | Stomach acid helps convert dietary iron into a form your gut can absorb. Long-term use of proton pump inhibitors and other acid reducers lowers that acid and, over time, can lower iron status. See PPIs and iron depletion. |
Deficiency Without Anemia — and the Testing Trap
Ferritin is the key test for iron status — it reflects how much iron you have stored, not just what's circulating that day. But there's a real gap between what labs flag as "deficient" and what actually causes symptoms. Standard lab cutoffs flag ferritin under roughly 12-15 ng/mL as deficient. In practice, many clinicians now treat ferritin under 30 ng/mL as functionally low in anyone with fatigue or other symptoms, because tissue-level iron depletion can start well before the number drops that far (PMID: 39110847).
That gap matters in practice. A ferritin of 18 ng/mL, for example, will usually come back on a lab report as "within normal range" — but it can still be low enough to leave someone tired, especially a menstruating woman. If your ferritin is in the teens or twenties and you have symptoms that fit, it's a reasonable thing to raise with your doctor rather than assume "normal" means "no issue" (PMID: 26222573).
How to Fix It
- Check whether you're actually in an at-risk group — menstruating (especially with heavy periods), pregnant, vegetarian or vegan, an endurance athlete, a frequent blood donor, dealing with GI blood loss, or on long-term acid-reducing medication. If none of these apply and you feel fine, routine testing usually isn't necessary.
- Get a ferritin test if you're at risk or have symptoms. It's the most useful single marker of iron status, more informative than hemoglobin alone.
- Push past a "normal" result if symptoms don't add up — a ferritin in the teens or twenties can still be functionally low even though the lab didn't flag it. See our guide to iron for anemia and low ferritin.
- Never supplement iron without a confirmed deficiency. Unlike water-soluble vitamins, your body has no efficient way to get rid of excess iron, so "just in case" supplementing is a real risk, not a harmless precaution.
- If you're confirmed low, treat it and retest. Compare ferrous sulfate vs. bisglycinate to pick a form you can actually tolerate for the months it takes to refill iron stores, then recheck ferritin rather than stopping once you feel better.
Which iron to buy, if you're confirmed deficient: A well-tolerated, low-cost option is Solgar Gentle Iron 25mg, a ferrous bisglycinate ("gentle iron") form that's far less likely to cause the constipation and nausea common with cheaper ferrous sulfate. Compare the full lineup by form, tolerability, and cost per day in our best iron supplement guide. But the form you pick matters far less than the first step: confirm a real deficiency with a ferritin test before taking anything.
Frequently Asked Questions
What are the first signs of low iron?
Fatigue and low energy are usually first, sometimes with pale skin, cold hands and feet, and brittle or spoon-shaped nails. Hair shedding, restless legs, trouble concentrating, and headaches can follow. These are easy to blame on stress or poor sleep, which is why testing beats symptom-matching.
Can you be iron deficient without anemia?
Yes. Ferritin can drop low enough to cause fatigue before hemoglobin falls into the anemia range. A randomized trial gave iron to non-anemic women with unexplained fatigue and low-normal ferritin, and the iron group improved significantly more than placebo. A normal blood count doesn't rule out low iron as a cause of tiredness.
Who is most at risk?
Menstruating women (especially with heavy periods), pregnant women, vegetarians and vegans, endurance athletes, frequent blood donors, people with GI blood loss, and long-term acid-reducer (PPI) users. Outside these groups, deficiency is genuinely uncommon.
What ferritin level counts as low?
Most labs flag ferritin under about 12-15 ng/mL as deficient. But many clinicians treat anything under 30 ng/mL as functionally low in someone with symptoms, since tissue iron can be depleted before the lab's flagged cutoff. A "normal" lab flag doesn't guarantee normal iron status.
Does coffee or tea block iron absorption?
Yes, meaningfully. Tannins and polyphenols in coffee and tea bind non-heme iron in the gut and reduce absorption, especially from plant foods and supplements. Separating either from iron-rich meals or supplements by an hour or two preserves more of the iron.
Related Guides
- Iron for Anemia & Low Ferritin — dosing and how long treatment takes
- Iron for Women — menstruation, pregnancy, and athletes
- Ferrous Sulfate vs. Bisglycinate — which form to buy
- Iron Dosage Guide — how much to take and the alternate-day trick
- Best Iron Supplement — ranked by form, tolerability, and cost per day
- PPIs and Iron Depletion — acid reducers and iron status
- Always Tired? — fatigue is a common but nonspecific low-iron symptom
- All Iron Guides
Sources
- Camaschella C. "Iron-Deficiency Anemia." N Engl J Med. 2015;373(5):485-486. PMID: 26222573
- Verdon F, Burnand B, Stubi CL, et al. "Iron Supplementation for Unexplained Fatigue in Non-Anaemic Women: Double Blind Randomised Placebo Controlled Trial." BMJ. 2003;326(7399):1124. PMID: 12763985
- Niriella MA, Jayasena H, Withanachchi A, Premawardhena A. "Mistakes in the Management of Iron Deficiency Anaemia: A Narrative Review." Hematology. 2024;29(1):2387987. PMID: 39110847
- Phan DM, Lam MY, Trang MN. "Iron Therapy & Restless Legs Syndrome: A Narrative Review." Sleep Breath. 2026;30(4). PMID: 42371291