Anemia grades: mild, moderate and severe anemia based on hemoglobin levels

The degree of anemia is a way to assess how much hemoglobin is reduced compared to age-related and physiological norms. Hemoglobin is the main laboratory indicator of anemia, but it does not explain the cause of the decrease: the same number can indicate iron deficiency, blood loss, vitamin B12 deficiency, chronic inflammation, kidney disease, hemolysis, or bone marrow disease. [1] [2]

In 2024, the World Health Organization updated its guidelines for hemoglobin thresholds for diagnosing anemia. It stated that thresholds depend on age, gender, and pregnancy status, and that the severity classification itself helps guide clinical management but does not replace the search for the cause of the anemia. [3] [4]

Mild anemia doesn't always mean "safe," and severe anemia doesn't always have the same consequences for all patients. Risk depends on the rate at which hemoglobin declines, age, pregnancy, heart and lung disease, kidney function, the presence of bleeding, and the body's ability to compensate for the lack of oxygen. [5] [6]

If hemoglobin levels decline slowly, a person may complain only of fatigue and decreased endurance for a long time. If hemoglobin levels decline rapidly, even moderate anemia can cause severe weakness, palpitations, shortness of breath, dizziness, and fainting. [7] [8]

Therefore, the degree of anemia should be considered together with the symptoms and tests: complete blood count, mean corpuscular volume, reticulocytes, ferritin, transferrin saturation, vitamin B12, folate, inflammatory markers, kidney function and signs of blood loss or hemolysis. [9]

What is being assessed?	Why is this necessary?
Hemoglobin	Determines the fact and degree of anemia
Hematocrit	Shows the proportion of red blood cells in the blood
Mean corpuscular volume	Helps differentiate between microcytic, normocytic and macrocytic anemia
Reticulocytes	Shows the bone marrow response
Ferritin and transferrin saturation	Helps identify iron deficiency
Vitamin B12 and folic acid	Needed for macrocytic anemia
Creatinine	Helps assess the contribution of kidney disease

Degrees of anemia by hemoglobin in adults, children and pregnant women

According to the updated World Health Organization guidelines, in non-pregnant women aged 15 to 65, anemia is defined as hemoglobin levels below 120 grams per liter, and in men aged 15 to 65, below 130 grams per liter. For pregnant women, the thresholds are lower: below 110 grams per liter in the first and third trimesters and below 105 grams per liter in the second trimester. [10]

The World Health Organization classifies anemia as mild, moderate, and severe. For adult non-pregnant women, mild anemia corresponds to a hemoglobin level of 110-119 grams per liter, moderate anemia corresponds to 80-109 grams per liter, and severe anemia corresponds to less than 80 grams per liter. For men, mild anemia corresponds to 110-129 grams per liter, moderate anemia corresponds to 80-109 grams per liter, and severe anemia corresponds to less than 80 grams per liter. [11]

In children, thresholds vary by age. For example, for children 6-23 months, anemia begins below 105 grams per liter, for children 24-59 months - below 110 grams per liter, for children 5-11 years - below 115 grams per liter, and for children 12-14 years - below 120 grams per liter. [12]

For pregnant women, the degree of anemia also depends on the trimester. In the 1st and 3rd trimesters, mild anemia corresponds to 100-109 grams per liter, moderate - 70-99 grams per liter, severe - below 70 grams per liter; in the 2nd trimester, mild anemia is 95-104 grams per liter, moderate - 70-94 grams per liter, severe - below 70 grams per liter. [13]

These figures are needed to standardize diagnostics, but treatment tactics are determined by more than just the degree. The World Health Organization emphasizes that the management of a person with mild, moderate, or severe anemia may vary depending on the clinical situation and the cause of the anemia. [14]

Group	No anemia	Mild anemia	Moderate anemia	Severe anemia
Women 15-65 years old, not pregnant	120 and above	110-119	80-109	below 80
Men 15-65 years old	130 and above	110-129	80-109	below 80
Pregnancy, 1st trimester	110 and above	100-109	70-99	below 70
Pregnancy, 2nd trimester	105 and above	95-104	70-94	below 70
Pregnancy, 3rd trimester	110 and above	100-109	70-99	below 70
Children 6-23 months	105 and above	95-104	70-94	below 70
Children 24-59 months	110 and above	100-109	70-99	below 70
Children 5-11 years old	115 and above	110-114	80-109	below 80

Why the degree of anemia does not equal the severity of the condition

The same hemoglobin level can be tolerated differently. A young person without chronic illnesses may have moderate anemia and complain only of weakness during exercise, while an elderly patient with coronary artery disease may experience shortness of breath, chest pain, and palpitations with a less profound decrease in hemoglobin. [15] [16]

The rate at which anemia develops is sometimes more important than the number itself. With a slow decline in hemoglobin, the body has time to partially adapt: the heart rate increases, blood flow distribution changes, and tissues better extract oxygen from the blood; in acute blood loss, these mechanisms are unable to protect the patient. [17]

The cause of anemia also changes the risk. Iron deficiency anemia requires a search for the source of iron deficiency, anemia of chronic inflammation requires treatment of the underlying disease, hemolytic anemia requires an assessment of red blood cell destruction, and anemia in chronic kidney disease requires a separate nephrological approach. [18] [19]

Severe anemia often produces symptoms even at rest. The Merck Manual notes that pallor becomes more typical in severe anemia, such as hemoglobin levels below 70 grams per liter, but physical signs of anemia alone are not sensitive or specific enough. [20]

Anemia cannot be assessed solely by a chart. A patient's complaints, physical examination, complete blood count with red blood cell indices, reticulocytes, iron levels, vitamin B12, folate, inflammatory markers, kidney function, and blood loss testing, if possible, are required. [21]

What changes the danger of anemia?	Why is this important?
Rapid drop in hemoglobin	The body does not have time to compensate for the lack of oxygen
Heart disease	Higher risk of ischemia and decompensation
Lung diseases	The decrease in blood oxygen capacity is more difficult to bear
Pregnancy	Risks to mother and fetus are important
Childhood	Age norms and developmental assessment are needed
Old age	There are often several causes of anemia at the same time.
Active bleeding	The pills work too slowly.

Mild anemia

Mild anemia often goes unnoticed or presents nonspecifically: fatigue, decreased endurance, drowsiness, impaired concentration, palpitations during exertion, or a feeling of "not having enough energy." But the absence of obvious symptoms doesn't mean the cause can be ignored. [22]

Mild anemia is particularly often associated with early iron deficiency, heavy menstrual bleeding, inadequate iron intake, early chronic inflammation, hidden gastrointestinal losses, or vitamin deficiencies. In men and postmenopausal women, even mild iron deficiency requires careful attention to potential blood loss. [23]

A primary battery of tests typically includes a complete blood count (CBC) with red blood cell indices, reticulocytes, ferritin, transferrin saturation, C-reactive protein, vitamin B12, folate, and creatinine. This battery helps differentiate deficiency anemia from inflammatory anemia, kidney disease, or other mechanisms. [24]

Mild anemia doesn't always require immediate treatment, but it does require a systematic explanation of the cause. It's inappropriate to simply prescribe "blood vitamins" without understanding what exactly is missing and whether there is ongoing blood loss. [25]

If mild anemia is detected by chance, it's helpful to compare the test results with previous ones. If hemoglobin has been stable for years, that's one thing; if it drops by 20-30 grams per liter in a short period, that's a reason to speed up the testing. [26]

Mild anemia: what's important	Practical meaning
May not produce symptoms	We still need to find the reason.
Often associated with iron deficiency	Ferritin and transferrin saturation are needed
In women, it may be associated with menstruation.	An assessment of the volume of blood loss is needed.
In men and women after menopause, it is alarming	We need to think about hidden blood loss.
It may be the first stage of a chronic disease.	Inflammation and kidney function are needed
Dynamic analysis is needed	The rate of hemoglobin decline is important

Moderate anemia

Moderate anemia often causes noticeable symptoms: weakness, shortness of breath during normal activity, palpitations, dizziness, decreased performance, tinnitus, cold extremities, and intolerance to physical activity. With chronic, slow progression, complaints may be less pronounced, but this does not make the condition harmless. [27] [28]

At this stage, it is especially important to understand the mechanism of anemia. Microcytic anemia requires testing for iron deficiency and sources of blood loss; macrocytic anemia requires testing for vitamin B12 and folic acid; normocytic anemia requires testing for inflammation, kidney disease, blood loss, hemolysis, and bone marrow disease. [29]

If moderate anemia is due to iron deficiency, treatment typically involves iron supplements and identifying the underlying cause. If chronic inflammation is the cause, simply prescribing iron may be less effective because the iron may be "locked" in stores and less available for hematopoiesis. [30]

Moderate anemia in an elderly patient, a pregnant woman, or someone with heart failure, chronic kidney disease, or coronary artery disease requires a more cautious assessment. In such patients, even a "not-so-low" hemoglobin level can be accompanied by clinically significant deterioration. [31]

If moderate anemia is detected along with black stool, blood in the stool, hematemesis, severe weakness, or a drop in blood pressure, it should not be treated as a planned deficiency. In such a situation, active blood loss and urgent examination should be considered. [32]

Moderate anemia: type of situation	What do they check?
Small red blood cells	Ferritin, transferrin saturation, source of blood loss
Large red blood cells	Vitamin B12, folic acid, liver, thyroid gland
Normal red blood cell size	Reticulocytes, kidneys, inflammation, hemolysis
Rapid decrease in hemoglobin	Blood loss or hemolysis
Old age	Several causes of anemia at the same time
Pregnancy	Trimester, iron, folic acid, vitamin B12

Severe anemia

Severe anemia is a condition in which the risk of complications is significantly higher, especially if hemoglobin has dropped rapidly or if there is heart disease, lung disease, kidney disease, pregnancy, or active bleeding. The World Health Organization classifies hemoglobin levels below 80 grams per liter in adults as severe anemia, and often below 70 grams per liter in pregnant women and young children, depending on the blood group. [33]

Symptoms of severe anemia may include shortness of breath at rest, severe weakness, palpitations, dizziness, fainting, chest pain or pressure, confusion, cold sweats, and a sharp decrease in exercise tolerance. These symptoms require urgent medical evaluation.[34][35]

In severe anemia, it is important not only to increase hemoglobin but also to quickly determine the cause. A repeat complete blood count, reticulocytes, blood smear, ferritin, transferrin saturation, vitamin B12, folate, bilirubin, lactate dehydrogenase, haptoglobin, creatinine, and a search for bleeding based on clinical signs are necessary. [36]

Red blood cell transfusion is not considered automatically, but rather based on the clinical situation. NICE recommends that, when using a restrictive strategy in stable patients, a threshold of 70 grams per liter and a target hemoglobin of 70-90 grams per liter after transfusion should be considered, unless there is major bleeding, acute coronary syndrome, or regular transfusion dependence. [37]

The 2023 AABB international guidelines also support a restrictive strategy in hemodynamically stable hospitalized adults, generally considering transfusion at hemoglobin levels below 70 grams per liter, but emphasize that other thresholds may be used in specific groups.[38]

Severe anemia: a sign	Why is this dangerous?
Shortness of breath at rest	Tissues receive little oxygen
Chest pain	Risk of myocardial ischemia
Fainting	Severe hypoxia or blood loss is possible.
Black chair	Possible gastrointestinal bleeding
Vomiting blood	Possible bleeding from the upper gastrointestinal tract
Jaundice and dark urine	Possible hemolysis
Decreased white blood cells and platelets	Possible bone marrow disease

Degrees of anemia in pregnant women, children and the elderly

In pregnant women, the degree of anemia is assessed by trimester, because during pregnancy, blood plasma volume increases and the normal hemoglobin range changes. In the second trimester, the anemia threshold is lower than in the first and third trimesters, which is reflected in the updated tables of the World Health Organization. [39] [40]

Anemia during pregnancy is important not only for the woman's well-being but also for obstetric risks. Even if anemia is mild, the doctor should assess iron deficiency, folate deficiency, vitamin B12 deficiency, nutrition, blood loss, and concomitant diseases. [41]

In children, the degree of anemia cannot be assessed using adult standards. For example, for children aged 6-23 months, the anemia threshold in 2024 was set at below 105 grams per liter, while for children aged 5-11 years it was below 115 grams per liter, and for adolescents aged 12-14 years it was below 120 grams per liter. [42]

In older adults, anemia is sometimes mistakenly considered a natural consequence of aging. In practice, decreased hemoglobin in an elderly patient requires investigation of iron deficiency, chronic inflammation, kidney disease, occult blood loss, vitamin deficiency, cancer, and bone marrow disorders. [43]

In patients with cardiovascular disease, the degree of anemia must be interpreted with particular caution. The AABB notes that for some patients, such as those with cardiovascular disease or after certain surgeries, clinicians may choose a higher transfusion threshold than 70 grams per liter. [44]

Group	Why the approach is different
Pregnant women	The threshold depends on the trimester, the risks for the mother and fetus are important
Children under 2 years old	Your age-related hemoglobin norms
Teenagers	Norms change with age and sexual development.
Elderly	There are often several causes of anemia.
Patients with heart disease	Symptoms may appear with lower hemoglobin levels.
Patients with kidney disease	Anemia is linked to iron, inflammation, and erythropoietin.

Diagnosis by degree of anemia

In mild anemia, testing can usually be done routinely if there are no alarming symptoms. This begins with a complete blood count, red blood cell indices, reticulocytes, ferritin, transferrin saturation, C-reactive protein, vitamin B12, folate, and creatinine. [45]

In moderate anemia, the diagnostic workup should be more active. It is necessary to determine the type of anemia based on the mean corpuscular volume, assess iron stores, rule out vitamin B12 and folate deficiency, and check for inflammation, kidney function, signs of hemolysis, and possible blood loss. [46]

In severe anemia, evaluation is often urgent. If there is shortness of breath at rest, chest pain, fainting, a drop in blood pressure, black stools, blood in the stool, or hematemesis, the patient's vital signs, possible blood loss, and the need for emergency care are assessed first. [47]

If the anemia is microcytic, the first line of investigation is iron metabolism and the cause of iron deficiency. If the anemia is macrocytic, vitamin B12, folate, blood smear, liver function tests, thyroid function, and medications are important. If the anemia is normocytic, reticulocytes, kidney function, inflammation, and hemolysis are particularly important. [48]

If anemia is accompanied by decreased white blood cell or platelet counts, unusual cells appear on a blood smear, frequent infections, bleeding, or bruising occur, a hematological evaluation is needed. This may indicate not just a simple iron deficiency, but a more serious hematopoietic disorder. [49]

Degree of anemia	Minimal diagnostic focus
Light	Confirm the type of anemia and find early deficiency
Moderate	Actively seek the cause and evaluate the symptoms
Heavy	Exclude blood loss, hemolysis, severe deficiency and the need for emergency assistance
Any degree with microcytosis	Ferritin, transferrin saturation, source of iron loss
Any degree with macrocytosis	Vitamin B12, folic acid, blood smear
Any grade with high reticulocyte response	Blood loss or hemolysis

Treatment depending on the degree of anemia

Treatment of anemia depends primarily on the cause, not just the severity. Iron deficiency anemia requires iron replacement and identification of the underlying cause, vitamin B12 deficiency requires vitamin B12 replacement therapy, folate deficiency requires folic acid, inflammatory anemia requires control of the underlying disease, and hemolysis requires specific diagnosis and treatment of the underlying cause of red blood cell destruction. [50]

Mild iron deficiency anemia is often treated with oral iron supplements unless there is malabsorption, intolerance, or ongoing significant blood loss. However, even mild iron deficiency anemia in a man or postmenopausal woman requires evaluation for possible gastrointestinal blood loss. [51]

For moderate anemia, treatment is usually initiated more quickly and the response is monitored. If hemoglobin does not increase despite appropriate therapy, the diagnosis, adherence to treatment, dosage, ongoing blood loss, inflammation, malabsorption, and kidney disease should be reconsidered. [52]

In severe anaemia, it is sometimes necessary not only to treat the underlying cause but also to temporarily restore the blood's oxygen capacity. NICE and AABB support restrictive transfusion strategies in stable patients, but emphasize that the decision depends on the clinical context, bleeding, cardiovascular risk, and symptoms. [53] [54]

During pregnancy, childhood, chronic kidney disease, and cardiovascular disease, treatment should be individualized. In these groups, the degree of anemia according to the table is helpful but does not replace the physician's clinical judgment. [55] [56]

Cause of anemia	The basic approach
Iron deficiency	Iron supplements and searching for the cause of deficiency
Vitamin B12 deficiency	Oral or intramuscular vitamin B12 due to deficiency
Folic acid deficiency	Folic acid after ruling out vitamin B12 deficiency
Chronic inflammation	Treatment of the underlying disease and assessment of iron availability
Chronic kidney disease	Iron, nephrological assessment, sometimes stimulation of hematopoiesis
Hemolysis	Finding and treating the cause of red blood cell destruction
Acute blood loss	Stopping bleeding, infusions, sometimes red blood cell transfusions

When anemia requires urgent help

Urgent care is needed for any degree of anemia, including chest pain or pressure, shortness of breath at rest, fainting, confusion, severe weakness, a drop in blood pressure, a rapid pulse, or signs of shock. These symptoms indicate that the body may not be able to deliver oxygen. [57] [58]

Seek immediate medical attention if you experience signs of bleeding: black stool, blood in the stool, vomiting blood, severe uterine bleeding, hemoptysis, sudden pallor, and rapid deterioration in health. In such cases, iron or vitamin tablets are not sufficient. [59]

Urgent evaluation is necessary for jaundice, dark urine, back or abdominal pain, a rapid decrease in hemoglobin, and high reticulocytes, as this may indicate hemolysis. Hemolytic anemia can progress rapidly and requires separate laboratory confirmation. [60]

If anemia is accompanied by low white blood cell and platelet counts, frequent infections, bleeding, bruising, unexplained fever, or unusual cells on a blood smear, urgent or expedited hematological testing is needed. This may be a sign of bone marrow dysfunction. [61]

Severe anemia in pregnant women, children, the elderly, or patients with heart or kidney disease requires a lower threshold for seeking help. These groups are less likely to tolerate the reduction in blood oxygen capacity and are more likely to experience complications. [62] [63]

Urgent sign	Possible cause of danger
Shortness of breath at rest	Insufficient oxygen supply
Chest pain	Risk of coronary heart disease
Fainting	Severe anemia, blood loss, or circulatory problems
Black chair	Gastrointestinal bleeding
Vomiting blood	Upper gastrointestinal bleeding
Jaundice and dark urine	Possible hemolysis
Low white blood cells and platelets	Possible bone marrow disease

Frequently asked questions

What are the different degrees of anemia? Typically, anemia is classified as mild, moderate, and severe. According to the World Health Organization classification, the degree depends on the hemoglobin level and the patient's group: adult male, non-pregnant woman, pregnant woman, or child of a certain age. [64]

What hemoglobin level is considered mild anemia in adults? In non-pregnant women aged 15 to 65, mild anemia corresponds to a hemoglobin level of 110-119 grams per liter, and in men aged 15 to 65, it is 110-129 grams per liter. [65]

What hemoglobin level is considered moderate anemia in an adult? In adult men and non-pregnant women aged 15 to 65 years, moderate anemia corresponds to a hemoglobin level of 80-109 grams per liter. [66]

What hemoglobin level is considered severe anemia in adults? In adult men and non-pregnant women aged 15 to 65, severe anemia is defined as a hemoglobin level below 80 grams per liter. The urgency of treatment depends on the symptoms, the rate of hemoglobin decline, and any associated illnesses. [67] [68]

Why do pregnant women have different degrees of anemia? During pregnancy, blood plasma volume increases, so hemoglobin levels may physiologically decrease. The World Health Organization uses different thresholds for the first, second, and third trimesters. [69]

Can mild anemia be treated with diet alone? Diet can sometimes help with early deficiency, but established iron deficiency anemia often requires iron supplements and an investigation into the underlying cause. In men and postmenopausal women, it is especially important to rule out occult blood loss. [70]

At what degree of anaemia does a blood transfusion become necessary? Transfusions are not prescribed based solely on the degree of anaemia. NICE and AABB generally consider a restrictive approach in stable patients, often with a threshold of around 70 grams per litre, but the decision depends on symptoms, bleeding, cardiovascular risk, and the overall situation. [71] [72]

Why can one person with moderate anemia walk normally, while another walks poorly? It all depends on the rate at which the anemia develops, age, heart and lung disease, level of physical activity, and the body's ability to compensate for the decrease in hemoglobin. A rapid decrease in hemoglobin is usually more difficult to tolerate than a slow one. [73]

What tests are needed to determine the cause of the degree of anemia? Typically, a complete blood count (CBC) with red blood cell indices, reticulocytes, ferritin, transferrin saturation, vitamin B12, folate, C-reactive protein, creatinine, and, if hemolysis is suspected, bilirubin, lactate dehydrogenase, haptoglobin, and a direct antiglobulin test are needed. [74]

When does anemia require urgent medical attention? Seek immediate medical attention if you experience shortness of breath at rest, chest pain, fainting, confusion, a drop in blood pressure, black stools, blood in vomit or stool, a rapid decrease in hemoglobin, jaundice, dark urine, or a combined decrease in white blood cells and platelets. [75] [76]

Key points from experts

The World Health Organization (WHO) updated its hemoglobin thresholds for diagnosing anemia in 2024, maintaining the same approach to classifying anemia as mild, moderate, and severe based on hemoglobin levels. The organization emphasizes that patient management depends not only on the severity but also on the cause and clinical situation. [77] [78]

Gloria F. Gerber, MD, Johns Hopkins School of Medicine, author of the Merck Manual on the Evaluation of Anemia: Anemia is a manifestation of the underlying disease, not a definitive diagnosis. Therefore, evaluation of the degree should be accompanied by a search for the cause through a complete blood count, reticulocyte count, blood smear, and additional tests. [79]

Jeffrey L. Carson, MD, professor of medicine, and the AABB International Group: In hemodynamically stable hospitalized adults, a restrictive transfusion strategy is generally recommended, with transfusion considered at hemoglobin levels below 70 grams per liter, but the clinical context remains crucial.[80]

NICE, National Institute for Health and Care Excellence (NICE): When considering a restrictive transfusion strategy in stable patients, a threshold of 70 grams per litre and a target haemoglobin of 70–90 grams per litre after transfusion is usually considered unless there is major bleeding, acute coronary syndrome or chronic transfusion dependence.[81]

Merck Manual experts: Symptoms of anemia depend on the severity and speed of development of the condition; slow anemia can take a long time to compensate, while a rapid decrease in hemoglobin causes more pronounced symptoms even at not very low numbers. [82]