FAQ: What do ASH's new ferritin thresholds mean for your patients?

The American Society of Hematology (ASH) issued new evidence-based guidelines on the diagnosis of iron deficiency, prepublished online in Blood Advances on September 16, 2026, and published in the November 10, 2026 issue.¹ ASH said the guidance addresses long-standing challenges such as variation in testing practices, inconsistent thresholds, and clinical scenarios in which iron deficiency can be difficult to identify, and it covers adults, young children, menstruating and pregnant individuals, and people with inflammation. The guidelines recommend higher ferritin thresholds to help clinicians identify iron deficiency earlier and more accurately.²

The guideline panel reached 5 recommendations using the GRADE approach, including conditional recommendations based on low or very low certainty in the evidence and 1 strong recommendation against a serum ferritin threshold of 15 ng/mL or lower in pregnant individuals. The panel included 1 maternal fetal medicine specialist, and the target audience includes obstetricians and gynecologists, as well as hematologists, family physicians, pediatricians, internists, advanced practice providers, and patients.¹

ASH said the recommended cutoffs are now higher across all populations, so some people previously considered not to have iron deficiency may meet the criteria, especially if their ferritin level was close to the old cutoff.²

1. What new serum ferritin thresholds did ASH recommend?

The thresholds vary by population. For infants and children aged 9 months to 4 years, the panel suggests 20 ng/mL or lower instead of 12 ng/mL or lower. For adults, menstruating individuals, and pregnant individuals, it suggests 30 ng/mL or lower, and it suggests against 15 ng/mL or lower in menstruating individuals and recommends against it in pregnant individuals. For adults with anemia of inflammation, it suggests evaluating both serum ferritin and transferrin saturation (TSAT) rather than serum ferritin alone.¹

A higher cutoff of 50 ng/mL or lower is considered appropriate in defined high-risk situations, such as heavy menstrual bleeding (HMB) or other abnormal uterine bleeding (AUB) with excessive blood loss, and may be appropriate for pregnant individuals with anemia. For adults with inflammation, ASH said diagnosis can be considered with serum ferritin under 100 ng/mL or TSAT under 20%.¹ ²

ASH cited an estimated 1 in 3 people affected by iron deficiency, including about 10 million adults in the U.S. and 2 billion people worldwide, with up to 70% of cases missed among high-risk populations because of limited screening and variability in diagnostic reference ranges.²

"Iron deficiency and iron deficiency anemia are among the most common yet neglected medical conditions globally," said ASH President Robert S. Negrin, MD. "Many patients live with symptoms such as fatigue, weakness, dizziness, or difficulty concentrating for months or even years before iron deficiency is recognized. These guidelines are an important step toward closing that gap by helping clinicians diagnose iron deficiency earlier and more accurately, so more patients can receive the care they need."²

2. What ferritin threshold applies to menstruating individuals?

For menstruating individuals, the panel suggests a serum ferritin threshold of 30 ng/mL or lower and suggests against 15 ng/mL or lower for diagnosing iron deficiency (conditional recommendation, low certainty in the evidence). A higher threshold of 50 ng/mL or lower is appropriate for people with HMB or other forms of AUB resulting in excessive blood loss, symptoms associated with iron deficiency, additional risk factors, upcoming surgery, or planning pregnancy.¹

A good practice statement says a detailed menstrual history is necessary to facilitate the diagnosis of AUB, particularly HMB, and that addressing identified abnormal bleeding or HMB would be essential. The panel noted that most people with iron deficiency from menstrual blood loss have a serum ferritin far lower than 50 ng/mL at diagnosis, and it recognized people with HMB as a particularly vulnerable subgroup.¹

The panel placed greater value on not missing a diagnosis, citing consequences in menstruating individuals that include progressive iron deficiency and anemia, major bleeding at gynecologic surgery, blood transfusion and red cell antigen alloimmunization that could complicate future pregnancies, fatigue, impaired cognition, altered mood, poor physical performance, and decreased health-related quality of life. It judged the undesirable effects of a threshold of 15 ng/mL or lower to be highest because of the high proportion of people with HMB in this population and the high risk of blood transfusion among those undergoing gynecologic surgeries. The evidence base included a systematic review of 79 studies (264,178 individuals) aged 12 to 45 years, with a pooled global prevalence of iron deficiency of 27%.¹

3. What ferritin threshold applies in pregnancy?

For pregnant individuals, the panel suggests a serum ferritin threshold of 30 ng/mL or lower (conditional recommendation, low certainty) and recommends against 15 ng/mL or lower (strong recommendation, low certainty). For pregnant individuals with anemia, with or without other iron deficiency risk factors or symptoms, 50 ng/mL or lower may be appropriate to diagnose iron deficiency and guide management.¹

The panel said that using 30 ng/mL or lower instead of 15 ng/mL or lower, at any gestational age, reduces both the risk of untreated iron deficiency during pregnancy and the risk of progression to iron deficiency anemia. It supported the 50 ng/mL or lower threshold in pregnant individuals with concomitant anemia to minimize progression of iron deficiency anemia in later trimesters and account for the fetus's reliance on maternal iron stores, but support was not unanimous for pregnant individuals without anemia because of uncertain benefits and potential harms of treatment at that threshold.¹

The pooled global prevalence of iron deficiency in pregnant individuals was 37%, based on 31 studies (93,782 individuals) across all trimesters. The panel noted that no data directly link maternal or neonatal outcomes to specific serum ferritin thresholds during pregnancy, and it said a higher threshold may help individuals with limited health care access receive iron supplementation before anemia develops.¹

4. Which pregnancy risk factors and outcomes did the panel consider?

The guideline lists pregnancy-specific risk factors for iron deficiency in the perinatal period: a preceding history of HMB, teenage pregnancy, hyperemesis gravidarum, multiple gestation, vaginal bleeding after the first trimester, abnormal placentation (placenta previa, placenta accreta spectrum, and placental abruption), a short interpregnancy interval (less than 18 months between delivery and subsequent conception), and multiparity.¹

Outcomes the panel weighed for pregnant individuals included maternal preterm delivery and postpartum hemorrhage, fetal cognitive development, fetal iron deficiency, low birth weight, and premature birth, along with treatment-related effects such as gastrointestinal adverse events with oral iron and infusion reactions or systemic infection with IV iron.¹

On the harms side, the panel noted that oral iron side effects may be amplified during pregnancy, acknowledged the time and financial burdens of IV iron, and described data on the benefits and harms of supplementation at higher ferritin thresholds as mixed. Iron supplementation in the setting of maternal hemoglobin above 13 g/dL was associated with preeclampsia and hypertensive disorders of pregnancy.¹

5. Does the guideline call for screening for iron deficiency in pregnancy?

Screening was outside the scope of the diagnostic recommendations, and the panel did not perform an evidence-based review focused on screening. However, the panel said it is reasonable to screen for iron deficiency by checking serum ferritin in all pregnant individuals, as well as other high-risk populations, with or without concomitant anemia.¹

The guideline notes that ACOG does not currently recommend routine screening for iron deficiency during pregnancy and that ACOG recommends a serum ferritin threshold of less than 30 ng/mL for diagnosing iron deficiency in pregnant people. The panel cited evidence that iron deficiency (defined as serum ferritin below 30 ng/mL) is pervasive in pregnancy regardless of anemia, said hemoglobin and mean corpuscular volume are inaccurate surrogates for iron sufficiency, and pointed to literature showing positive effects of early iron repletion in nonanemic pregnant individuals.¹

A 2026 joint clinical report from AAP and the American Society of Pediatric Hematology/Oncology recommends universal screening for both anemia and iron deficiency in all young children and in all menstruating individuals after the onset of menarche.¹

6. How does the guideline address children, adolescents, and other adults?

For infants and children aged 9 months to 4 years without known or suspected inflammation, the panel suggests 20 ng/mL or lower rather than 12 ng/mL or lower (conditional recommendation, low certainty). For children older than 4 years until adolescence (defined as age 11 years or older per AAP), 20 ng/mL or lower is appropriate by indirectly applying evidence for young children, and for nonmenstruating adolescents, 30 ng/mL or lower is appropriate by indirectly applying evidence from menstruating adolescents and adults. Menstruating adolescents follow the recommendation for menstruating individuals.¹

For adults other than menstruating or pregnant individuals, the panel suggests 30 ng/mL or lower instead of 15 ng/mL or lower, and 50 ng/mL or lower is appropriate for people with signs or symptoms associated with iron deficiency or ongoing risk factors, in those without known or suspected inflammation. Listed symptoms include fatigue, decreased quality of life, decreased cognitive function, restless legs syndrome, pica or pagophagia (ice craving), and decreased exercise tolerance. Pooled global prevalence estimates were 30% in young children and 16% in nonmenstruating, nonpregnant adults.¹

7. How should iron deficiency be evaluated in adults with inflammation?

For adults with anemia of inflammation, the panel suggests performing both serum ferritin and TSAT rather than serum ferritin alone (conditional recommendation, very low certainty). Iron deficiency may be considered when TSAT is under 20% or serum ferritin is under 100 ng/mL, and anemia of inflammation may occur with inflammatory bowel disease, infectious diseases, cancer, chronic kidney disease, heart failure, rheumatologic disorders, and other inflammatory disorders.¹ ²

TSAT should be drawn in a fasting state of 5 to 9 hours, including fasting from multivitamin or iron supplements, because the test is susceptible to recent dietary intake. Serum ferritin is an acute-phase reactant, so it may be falsely normal or elevated in the setting of inflammation. A good practice statement adds that anemia of inflammation may coexist with other causes of anemia and that results should be interpreted in the context of the full clinical picture and existing guidelines for chronic diseases. No recommendation was made for children with inflammation because of a lack of data.¹

In pooled evidence from 2 cross-sectional studies (67 individuals), serum ferritin alone below 100 ng/mL had a sensitivity and specificity of 0.38 and 0.88, respectively, while serum ferritin below 100 ng/mL and/or TSAT below 20% had a sensitivity and specificity of 0.91 and 0.70, respectively.¹

8. Why did the panel favor higher thresholds despite low-certainty evidence?

The panel placed greater value on avoiding missed diagnoses (false negatives) than on avoiding false positives. In pooled diagnostic accuracy data from 17 cross-sectional studies (5,327 individuals), a serum ferritin of 15 ng/mL or lower had a sensitivity and specificity of 0.41 and 0.99, 30 ng/mL or lower had 0.67 and 0.96, and 50 ng/mL or lower had 0.89 and 0.86. The panel judged that 30 ng/mL or lower best balanced false negatives and false positives, noting that false positives could lead to unnecessary iron supplementation and, in adults, potentially unnecessary evaluation such as bidirectional endoscopy.¹

The panel also reviewed WHO thresholds of below 12 ng/mL for children and below 15 ng/mL for otherwise healthy adults, which it described as highly specific but with low sensitivity. It said existing laboratory reference intervals are biased toward lower values because they were built from studies of apparently healthy people, a portion of whom were iron deficient, and it attributed the low certainty of evidence in part to a lack of research on the impact of therapy on clinical outcomes, which does not imply that such effects do not exist.¹

"These updated ferritin thresholds provide clear guidance in an area where consensus has been lacking," said guideline chair Jacquelyn M. Powers, MD, MS, section chief of hematology at Texas Children's Hospital and associate professor in the department of pediatrics at Baylor College of Medicine. "We hope these recommendations empower patients to better understand and ask for the testing they need and that health systems adopt these thresholds for diagnosis."²

9. What laboratory issues affect how ferritin results are interpreted?

Different assays can report different serum ferritin values for the same sample, with variability most pronounced at the higher end of the range. Data from 97 laboratories assessed by the Institute for Quality Management in Healthcare in Canada showed differences from the all-methods mean of plus or minus 30% to 40% at ferritin values below 50 ng/mL, meaning a ferritin of 10 ng/mL could range from 7 to 14 ng/mL across laboratories and a ferritin of 30 ng/mL could range from 21 to 42 ng/mL.¹

The panel suggested that laboratories convert from a laboratory-defined lower limit of normal (LLN) to a clinical decision limit (CDL) for the recommended thresholds, so that results at or below the threshold are flagged as abnormal regardless of the reference range, and that a comment accompany the postanalytical test report to facilitate implementation. It said use of an LLN contributes to underrecognition because reference ranges vary between laboratories and can classify values consistent with iron deficiency as within range. Serum ferritin is also ideally tested during an individual's baseline state of health.¹

10. What should clinicians tell patients, and what research gaps remain?

ASH said individuals should talk with their doctor about having ferritin tested according to the new cutoffs, especially if they are at higher risk, because some people previously told they did not have iron deficiency may now meet the criteria, particularly if their ferritin was close to the old cutoff. Higher-risk individuals include those who are pregnant or menstruating, children, and people with gastrointestinal conditions, dietary restrictions, blood loss, or other chronic conditions.² The guideline states that it is not intended to serve as a standard of care and that clinicians must make decisions based on each patient's clinical presentation, ideally through a shared process that considers the patient's values and preferences.¹

For menstruating individuals, the panel's research priorities include randomized clinical trials comparing patient-important outcomes using different ferritin thresholds, cost-effectiveness studies that include the 50 ng/mL threshold, and exploration of health equity implications. For pregnancy, priorities include the relationship between serum ferritin and TSAT across gestational stages and trimesters, outcomes related to ferritin testing including the optimal gestational timing for screening and treatment, randomized trials and prospective comparison of patient-important outcomes, cost-effectiveness studies, and health equity implications for maternal and fetal outcomes.¹

References:

1. Powers JM, Lim MY, Achebe MO, et al. American Society of Hematology 2026 guidelines for diagnosis of iron deficiency. Blood Adv. 2026;10(21):7353-7374. Prepublished online September 16, 2026. Accessed September 18, 2026. doi:10.1182/bloodadvances.2025015950

2. American Society of Hematology. ASH sets new standards for diagnosing iron deficiency. Press release. Published September 16, 2026. Accessed September 18, 2026. https://www.hematology.org/news-and-media/press-releases/2026/ash-sets-new-standards-for-diagnosing-iron-deficiency