What Are the WHO Guidelines for Anemia?

The World Health Organization defines anemia using hemoglobin concentration thresholds that vary by age, sex, and pregnancy status, with separate guidance on how to measure iron stores, when to supplement, and how to adjust readings for factors like altitude and smoking. These thresholds have been the global standard for decades, though WHO recently began updating them based on newer evidence and broader population data. The guidelines go well beyond a single diagnostic number and encompass prevention strategies, fortification policy, and special rules for settings where infections like malaria are common.

The Core Hemoglobin Thresholds

At sea level, WHO classifies anemia when hemoglobin falls below these cutoffs: less than 13.0 g/dL for men aged 15 and older, less than 12.0 g/dL for non-pregnant women aged 15 and older, less than 11.0 g/dL for pregnant women, less than 11.0 g/dL for children aged 6 to 59 months, less than 11.5 g/dL for children aged 5 to 11, and less than 12.0 g/dL for children aged 12 to 14. These numbers were originally proposed in 1968, based largely on studies of white European and North American adult populations.

WHO also grades severity. For non-pregnant adults, mild anemia falls between 11.0 and the relevant sex-specific threshold, moderate anemia ranges from 8.0 to 10.9 g/dL, and severe anemia is anything below 8.0 g/dL. For pregnant women, the severe cutoff is below 7.0 g/dL, moderate sits between 7.0 and 9.9 g/dL, and mild ranges from 10.0 to 10.9 g/dL.¹ The severe anemia threshold of 7.0 g/dL in children is especially important in field settings, where it triggers immediate referral and treatment.²

Why the Guidelines Are Being Updated

The 1968 thresholds have drawn criticism for years. They were derived from a narrow demographic and do not account for the natural variation in hemoglobin across different ethnic groups, geographies, and genetic backgrounds. WHO acknowledged this and launched a formal review process. The updated guidelines address hemoglobin concentrations for defining anemia at sea level and at high altitudes, along with the methodology for establishing normal reference ranges.³ A WHO technical meeting also concluded that the current thresholds needed revision and that the organization would undertake a broader global project to redefine them.⁴

The changes have practical consequences, particularly for countries at high elevations. Peru, for example, has large populations living above 3,000 meters. Whether those people are classified as anemic or healthy depends entirely on how altitude adjustments are calculated, which directly affects how many people qualify for public nutrition programs and how resources get allocated.

Adjustments for Altitude and Smoking

Hemoglobin naturally rises at higher altitudes because the body compensates for thinner air by producing more red blood cells. If you applied the sea-level cutoff to someone living at 4,000 meters, you would underestimate anemia in that population. WHO has long recommended subtracting an adjustment value from a person’s measured hemoglobin before comparing it to the standard threshold. The updated guidelines recalculate these adjustments at 500-meter intervals, and the revised numbers differ from the older formula that the U.S. CDC published in 1989.⁵

Smoking also raises hemoglobin, because carbon monoxide binds to hemoglobin and reduces its ability to carry oxygen, prompting the body to make more. WHO recommends adjusting hemoglobin downward for smokers, and the size of the adjustment varies with how many cigarettes a person smokes per day. The same reexamination study calculated these adjustments based on the mean hemoglobin difference between smokers and nonsmokers, stratified by cigarette quantity.⁵ Without these corrections, a heavy smoker living at high altitude could appear to have normal hemoglobin while actually being iron-depleted.

Ferritin Thresholds and Iron Stores

Hemoglobin tells you whether someone is anemic right now. Ferritin tells you whether their iron stores are running low, which predicts whether anemia is coming. WHO has traditionally defined depleted iron stores as serum ferritin below 12 µg/L in young children and below 15 µg/L in women of reproductive age. Those numbers came from expert opinion decades ago and were based on older laboratory methods.

Newer research suggests those cutoffs are too low. A study using data from a large U.S. national health survey found that physiologically based ferritin thresholds, identified by looking at when hemoglobin and other functional markers of iron actually start to drop, are closer to 20 µg/L in children and 25 µg/L in women.⁶ The implication is that the current WHO ferritin thresholds catch iron deficiency only at a fairly advanced stage, missing earlier depletion that a higher cutoff would flag. This matters for screening programs, because the goal of population-level screening is to intervene before hemoglobin actually drops into the anemia range.

When Inflammation Skews the Numbers

Ferritin has a catch: it is also an acute-phase protein, meaning it rises during infection and inflammation regardless of how much iron someone has stored. In populations with high rates of malaria, respiratory infections, or chronic inflammatory conditions, raw ferritin values can look reassuringly normal even when iron stores are genuinely depleted. WHO guidance recognizes this problem, and the BRINDA project (Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia) developed methods to correct ferritin readings using inflammation markers like C-reactive protein and alpha-1-acid glycoprotein.

The corrections make a real difference. Depending on the adjustment method used, the estimated prevalence of depleted iron stores in preschool children increased by 7 to 25 percentage points compared with unadjusted values. In women of reproductive age, the increase was 2 to 8 percentage points.⁷ In countries where infectious disease is widespread, failing to apply these corrections means underestimating how many people are iron-deficient, which in turn means underinvesting in supplementation and fortification programs.

Anemia in Pregnancy

Pregnant women get their own thresholds because blood volume expands substantially during pregnancy, naturally diluting hemoglobin. WHO defines anemia in pregnancy as hemoglobin below 11.0 g/dL. In practice, some clinical guidelines use a slightly lower cutoff of 10.5 g/dL during the second trimester, when the dilution effect peaks.⁸ The distinction matters because iron demands roughly double during pregnancy, and many women enter pregnancy with marginal iron stores that cannot keep up.

The consequences of untreated maternal anemia are serious. Beyond the increased risk of preterm delivery and low birth weight that clinicians have recognized for decades, recent neuroimaging research shows that maternal anemia is associated with measurable differences in infant brain structure. A South African study found altered brain volumes in young children whose mothers were anemic during pregnancy, with the association persisting after accounting for other risk factors.¹

Infants and Children

Iron deficiency anemia in the first two years of life carries outsized consequences compared with later ages. Infants who become iron-deficient during the period of rapid brain development show impaired learning and memory function that can persist even after hemoglobin normalizes.⁹ This is why WHO applies the anemia threshold of 11.0 g/dL starting at six months, when the iron a full-term infant received from the mother begins to run out and dietary intake needs to take over.

For infants younger than six months, the picture gets complicated. WHO does not provide universal cutoffs for this age group because hemoglobin fluctuates dramatically in the first weeks of life as fetal hemoglobin is replaced. Hospitals typically use locally developed, age-specific reference ranges for newborns and very young infants.¹

Iron Supplementation Recommendations

WHO does not simply diagnose anemia and stop there. The guidelines include specific supplementation strategies for populations at risk. For women of reproductive age in settings where anemia prevalence exceeds 20%, WHO recommends weekly iron and folic acid supplementation rather than daily dosing. The rationale is that weekly supplementation is easier to sustain over months and causes fewer gastrointestinal side effects, which improves adherence. The recommended dose is 60 mg of elemental iron plus 2.8 mg of folic acid, taken at least once per week for three months, repeated twice yearly or aligned with school terms.¹⁰

This weekly approach coexists with daily supplementation during pregnancy, where the iron demands are higher and the window for intervention is shorter. The two strategies are complementary: weekly supplementation before pregnancy builds up stores, and daily supplementation during pregnancy prevents depletion during the most critical period.

Special Rules for Malaria-Endemic Areas

Iron supplementation in regions with high malaria transmission has been one of the most contentious areas of WHO guidance. A large trial in Zanzibar in the early 2000s raised alarm when children given iron and folic acid supplements showed higher rates of hospitalization and death in a setting without reliable malaria prevention. That finding led WHO and UNICEF to issue a 2006 joint statement advising that iron supplementation in high-malaria settings should be targeted only at children who are confirmed anemic or iron-deficient, rather than given universally.¹¹

Subsequent systematic reviews have refined this picture. Iron supplementation alone does not appear to increase clinical malaria risk, and iron with or without folate is safe where malaria prevention or treatment programs are in place. The danger comes specifically from iron plus folate in settings where neither antimalarial prevention nor treatment is available.¹² The practical takeaway is that iron supplementation for anemic children remains recommended in malaria zones, but only if malaria is being adequately diagnosed and treated. Universal supplementation without malaria control is not safe.

Deworming as Part of the Strategy

Hookworm and other soil-transmitted helminths are a major but often overlooked driver of anemia in low-income countries. These parasites feed on blood in the intestinal wall, and chronic infection can drain iron faster than diet or supplements can replace it. WHO guidelines for anemia control in endemic areas recommend combining intermittent iron-folic acid supplementation with regular deworming. A 54-month program studying this combined approach in women of reproductive age found it effective at reducing anemia, iron deficiency, and helminth infections together.¹³ Supplementation without deworming in heavily infected populations treats the symptom while leaving the cause intact.

Food Fortification Guidelines

Beyond individual supplementation, WHO collaborates with other agencies to issue guidelines on iron fortification of staple foods, particularly wheat flour. The recommended fortification compound and dose depend on how much flour a population eats per day and the type of flour being used. For populations consuming 150 to 300 grams of low-extraction wheat flour daily, WHO recommends adding 20 parts per million of iron as NaFeEDTA, or 30 parts per million as dried ferrous sulfate or ferrous fumarate. For high-extraction flour, which contains more phytic acid that blocks iron absorption, NaFeEDTA is the only compound recommended because it resists that inhibition.¹⁴

These fortification strategies are designed to work at the population level, gradually improving iron status across an entire country without requiring individuals to take a pill. Many national flour fortification programs, however, were found to be using iron compounds or doses below the recommended levels, which limits their effectiveness.

How Blood Is Collected Matters

A detail that rarely makes it into public discussions of anemia guidelines is that the way blood is drawn can change results. WHO thresholds were established using venous blood (drawn from a vein in the arm), but many field surveys and screening programs in low-resource settings use capillary blood (a finger prick), because it requires less training and equipment. Capillary hemoglobin tends to run slightly higher than venous in most studies, though the difference is not always consistent.¹⁵

A study in adolescent girls found strong overall concordance between pooled capillary and venous hemoglobin, with similar anemia prevalence estimates at the population level. But at the individual level, agreement was only moderate: among girls classified as anemic by either blood source, only about 59% were identified by both methods.¹⁶ For a national survey estimating how common anemia is, the sampling method may not change the headline number much. For an individual being screened, it can mean the difference between being flagged for treatment or sent home.

Distinguishing Iron Deficiency From Other Causes

Not all anemia is caused by iron deficiency, and treating the wrong type with iron supplements is at best useless and at worst harmful. Thalassemia trait, a common inherited condition in many parts of the world, produces small red blood cells and mild anemia that can look almost identical to iron deficiency on a basic blood count. Various mathematical formulas have been developed to help distinguish the two conditions using simple lab values. An evaluation of these formulas found that the best-performing ones still misclassify roughly 30% of thalassemia carriers who also have another cause of anemia.¹⁷ In resource-limited settings where genetic testing is unavailable, these formulas can help prioritize who needs further workup, but they are not a replacement for definitive diagnosis.

WHO guidelines acknowledge that anemia has multiple causes, including folate and vitamin B12 deficiency, chronic disease, and genetic hemoglobin disorders. The hemoglobin threshold tells you someone is anemic; it does not tell you why. Effective anemia control programs need to investigate the cause, particularly in populations where thalassemia or sickle cell trait is common, before defaulting to iron supplementation.

Progress Toward Global Targets

In 2012, the World Health Assembly set a target of reducing anemia prevalence in women of reproductive age by 50% by 2025. An analysis of 15 low- and middle-income countries found that none of them was on track to meet that goal.¹⁸ The reasons vary by country but tend to cluster around the same themes: inadequate supplementation coverage, flour fortification programs that underperform because of poor enforcement, persistent parasitic infections, and the difficulty of addressing non-nutritional causes of anemia like chronic inflammation and genetic hemoglobin disorders through nutrition programs alone.

The WHO guidelines themselves are only as useful as the health systems that implement them. A country can adopt every recommended threshold, adjustment, and supplementation protocol, and still fail to reduce anemia if the drugs do not reach clinics, if the flour mills do not add enough iron, or if malaria control programs are underfunded. The gap between guideline and outcome is, in many settings, the more pressing problem than whether the hemoglobin cutoff is set at the right number.

Point-of-Care Testing in the Field

Implementing WHO guidelines in rural and remote areas depends on portable devices that can measure hemoglobin without a full laboratory. The two most widely used point-of-care devices are the HemoCue and the newer Aptus system, both of which use a small drop of blood from a finger prick. The Aptus can display results against WHO reference ranges, with corrections for age, sex, pregnancy, and altitude built into its software.² Field accuracy does not match laboratory-grade hematology analyzers perfectly, but for screening purposes, these devices make it possible to identify severe anemia on the spot and refer children or pregnant women for treatment the same day, rather than waiting weeks for lab results that may never come back.

The practical reality of anemia screening in low-resource settings is that some imprecision in measurement is an acceptable tradeoff for reaching people who would otherwise go undiagnosed entirely. The WHO guidelines are designed with this in mind: the thresholds are meant to be applied with the tools available, not reserved for ideal laboratory conditions that most of the world’s anemic population will never encounter.