A Ferritin of 30 or Lower: The New ASH Cutoffs for Diagnosing Iron Deficiency
Many people have left an appointment feeling worn out, told their iron was fine, with a ferritin that came back at 18 or 22. As of September, the American Society of Hematology (ASH) would call most of those results iron deficiency. Its new guideline raises the ferritin cutoffs for diagnosis across every group it covers.
What the ASH guideline recommends
Ferritin is a blood protein that doctors use to estimate how much iron the body has stored. ASH, a professional society of blood specialists, convened a panel from several medical specialties, including one patient representative. The panel carried out systematic reviews of the research on iron deficiency rates and diagnostic thresholds, and it graded the strength of that evidence using a standard method called GRADE [1]. A systematic review gathers the published studies on a question using search rules set in advance. The panel agreed on five recommendations, and one of their stated goals was to diagnose iron deficiency whether or not a person has anemia [1].
The cutoffs, as ASH summarized them, are [2]:
Children aged 9 months to 4 years: ferritin of 20 ng/mL or lower.
Adults, including people who menstruate and people who are pregnant: 30 or lower.
Heavy menstrual bleeding, or pregnancy with anemia: 50 or lower.
Adults with inflammation from conditions such as cancer, inflammatory bowel disease, or infection: below 100, with a transferrin saturation under 20% as an alternative test.
Transferrin is the protein that carries iron in the blood, and transferrin saturation is the percentage of it that is loaded with iron. ASH noted that some people who were told they did not have iron deficiency may now meet the definition, particularly those whose ferritin was near the old cutoff. Guidance on treatment is expected in 2027 [2].
Where the old ferritin cutoffs came from
Many labs and clinicians have used the World Health Organization thresholds: below 15 for women and below 12 for young children. Those numbers were set by expert opinion [3]. Researchers at the Centers for Disease Control and Prevention went looking for the ferritin level at which the body starts to struggle. Using US national survey data, they found that hemoglobin begins to fall, and a second marker of iron-starved red blood cell production begins to rise, at a ferritin of about 25 in non-pregnant women and about 20 in young children [3]. In a follow-up analysis of older national data, the researchers concluded that the WHO cutoffs identify a later, more severe stage of iron deficiency [4].
When researchers applied the same approach to 18,251 women and children in 12 countries across Africa, Asia, Europe, and Central America, the thresholds they found were consistent from country to country [5]. By those thresholds, 36% of the women had iron deficiency, compared with 20% under the WHO cutoff [5].
Even by the old standard, iron deficiency is common in the United States. Across US national surveys from 1999 to 2023, 17.3% of non-pregnant women aged 20 to 45 had a ferritin below 15, and iron deficiency anemia roughly doubled over that period, from 4.3% to 9.1% [6].
Finding the reason behind a low ferritin
A ferritin result is an estimate of stored iron. From a naturopathic point of view, the next question is why the stores are low. The usual reasons fall into three groups: losing iron, absorbing too little, and taking in too little. Heavy periods are common enough that ASH set a separate, higher cutoff for them [2]. Acid-suppressing medication is one absorption factor with data behind it. In a large UK study, people who had taken it continuously for a year or more had about 3.6 times the odds of iron deficiency compared with non-users [7]. That study was observational: the researchers compared people's existing records and did not assign anyone the medication, so it cannot prove the medication caused the deficiency. The authors pointed out that low stomach acid is an established cause of iron deficiency, so the connection makes sense [7].
Diagnosing iron deficiency before anemia appears also has support from a randomized trial. In a French trial of 198 menstruating women with unexplained fatigue, normal hemoglobin, and a ferritin below 50, twelve weeks of iron reduced fatigue scores by 47.7%, compared with 28.8% on placebo [8]. Iron did not change quality of life, depression, or anxiety scores in that trial [8]. That is a good reason to check ferritin when someone is tired and their blood count comes back normal.
Bringing the new cutoffs to your next blood test
These points can make your next conversation about iron more productive:
The number is more useful than the word "normal." If you have had ferritin tested, you can ask for the actual value and compare it with the ASH cutoffs above. A result described as normal a year ago could fall under the new cutoffs [2].
Heavy periods and pregnancy carry a higher cutoff. If either applies to you, two things to ask your doctor about are adding a ferritin test to your next round of bloodwork and which cutoff they use [2].
A low result deserves an explanation. Blood loss, absorption, and diet are all part of the workup. If you take acid-suppressing medication, tell your prescriber how long you have been on it, since long-term use was linked to iron deficiency in the UK study [7].
Testing comes before supplementing. Starting iron on a guess leaves you without a baseline. In the French fatigue trial, the authors suggested rechecking blood markers after six weeks of treatment to see if it was working [8].
References
Powers JM, Lim MY, Achebe MO, et al. American Society of Hematology 2026 guidelines for diagnosis of iron deficiency. Blood Adv. 2026. PMID: 42747316. doi:10.1182/bloodadvances.2025015950
Original article (press release, used for the specific thresholds): American Society of Hematology. "ASH Sets New Standards for Diagnosing Iron Deficiency." September 16, 2026. https://www.hematology.org/newsroom/press-releases/2026/ash-sets-new-standards-for-diagnosing-iron-deficiency
Mei Z, Addo OY, Jefferds ME, Sharma AJ, Flores-Ayala RC, Brittenham GM. Physiologically based serum ferritin thresholds for iron deficiency in children and non-pregnant women: a US National Health and Nutrition Examination Surveys (NHANES) serial cross-sectional study. Lancet Haematol. 2021;8(8):e572-e582. PMID: 34329578. doi:10.1016/S2352-3026(21)00168-X
Mei Z, Addo OY, Jefferds MED, et al. Comparison of current World Health Organization guidelines with physiologically based serum ferritin thresholds for iron deficiency in healthy young children and nonpregnant women using data from the Third National Health and Nutrition Examination Survey. J Nutr. 2023;153(3):771-780. PMID: 36803577. doi:10.1016/j.tjnut.2023.01.035
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. Lancet Glob Health. 2025;13(5):e831-e842. PMID: 40288394. doi:10.1016/S2214-109X(25)00009-9
Xiao MZX, Bentley J, Leavitt AD, Butwick AJ. Trends in anemia and iron deficiency among nonpregnant U.S. women of reproductive age, 1999-2023. Obstet Gynecol. 2026;148(2):269-277. PMID: 41926767. doi:10.1097/AOG.0000000000006277
Tran-Duy A, Connell NJ, Vanmolkot FH, et al. Use of proton pump inhibitors and risk of iron deficiency: a population-based case-control study. J Intern Med. 2018;285(2):205-214. PMID: 30141278. doi:10.1111/joim.12826 (Yggdrasil abstract library)
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):1247-1254. PMID: 22777991. doi:10.1503/cmaj.110950 (Yggdrasil abstract library)
This post is for education only and is not medical advice. Iron deficiency has many possible causes, and both too little and too much iron can cause problems, so please talk with your own provider before starting or changing an iron supplement.
If this resonates with what you're experiencing and you'd like to explore a naturopathic approach, book a consultation with our clinic.
Comments