I take iron tablets but my hemoglobin is not improving — why?

There are several common reasons. First, iron absorption can be limited — iron is best absorbed on an empty stomach, but many people find it causes nausea and take it with food, which reduces absorption. Calcium, tea, and coffee also interfere. Second, the anaemia may not be purely iron-deficient — B12 or folate deficiency, thalassaemia trait, chronic inflammation, or gut conditions all need different treatment. Third, the iron preparation or dose may not be right. After 2–3 months on adequate iron without improvement, doctors usually re-evaluate the cause.

Why is anaemia so common in Indian women?

Several factors combine. Vegetarian diets common in India provide less bioavailable iron than animal-source diets. Menstrual loss across reproductive years is a steady iron drain. Repeated and closely-spaced pregnancies are common, and each pregnancy demands large amounts of iron. Long-term B12 and folate deficiency is widespread in vegetarian populations. Underlying chronic conditions (infection, gut absorption issues) add further. The 2019–21 NFHS-5 survey reported about 57% of non-pregnant women in India below the WHO anaemia cut-off — a substantially higher rate than most other countries.

Should I be tested for thalassaemia trait?

Thalassaemia trait is more common in some Indian communities (notably people of Sindhi, Gujarati, Punjabi, Bengali, or some south-Indian heritage). It causes mild persistent anaemia with strikingly low MCV but normal or high iron stores. Testing — usually by hemoglobin electrophoresis (HPLC) — becomes important during pregnancy planning, when iron supplementation has not improved low Hb with low MCV, or when there is a family history. Both partners testing matters before conception because if both carry the trait, the baby can inherit the more serious thalassaemia major.

Do I need to fast for a hemoglobin test?

No — hemoglobin does not change meaningfully with recent meals. But because hemoglobin is usually part of a CBC drawn alongside other tests (some of which need fasting — lipids, sugars), an overnight fast is commonly requested for the broader panel. Stay normally hydrated. Recent intense exercise in the few hours before the test can transiently shift several CBC values.

Can vegetarians keep good hemoglobin without supplementation?

Many vegetarians do — but it requires attention. Plant-source iron (non-heme iron) is less efficiently absorbed than animal-source iron, so vegetarian diets need higher total intake and absorption-enhancing pairing (vitamin C–rich foods with iron-rich foods; avoiding tea/coffee with meals). Many Indian vegetarians, especially women of reproductive age, still benefit from periodic iron status monitoring and supplementation under medical guidance. B12 specifically is very difficult to get from a pure vegetarian diet without supplements or fortified foods.

Hemoglobin Test: Normal Range & Anaemia

Also seen on reports as: Hb, Hgb, Haemoglobin

What is Hemoglobin?

Hemoglobin (Hb) is the iron-containing protein inside red blood cells that picks up oxygen in the lungs and delivers it to every tissue in the body. The level of hemoglobin in blood is one of the most clinically used numbers on the Complete Blood Count (CBC) and is the standard way to diagnose anaemia.

Each red blood cell contains many hemoglobin molecules, so anaemia means either fewer red cells, smaller red cells with less hemoglobin each, or a combination — depending on the underlying cause. The cause of low hemoglobin matters more than the number alone, because the treatment is different for iron-deficiency anaemia, B12/folate-deficiency anaemia, thalassaemia trait, and anaemia of chronic disease.

The test is run on a small blood sample drawn from a vein, usually as part of a CBC. NABL-accredited Indian labs report hemoglobin in grams per decilitre (g/dL). Some clinical settings use point-of-care hemoglobinometers (HemoCue and similar) for faster screening — these can sometimes be slightly different from lab values.

Why doctors order it

Hemoglobin is ordered as part of almost every blood-test panel in India — routine health checks, antenatal screening (mandatory at each visit), pre-operative work-up, and any work-up of tiredness, breathlessness, or pallor. It is also screened in school health programs, blood-donation eligibility, and as part of major government anaemia-control programs like Anaemia Mukt Bharat.

Because anaemia is so widespread in India (NFHS-5 reported around 57% of non-pregnant women and 67% of children below WHO cut-offs), hemoglobin testing is the cornerstone of population-level anaemia control as well as individual care. Indian guidelines recommend periodic screening across the life course — particularly in women of reproductive age, pregnant women, children, and the elderly.

Hemoglobin is also monitored in chronic conditions that affect red-cell production or survival — chronic kidney disease (the kidneys make erythropoietin, which the bone marrow needs to make red cells), inflammatory conditions, cancer treatment, certain medications, and known thalassaemia trait or other haemoglobinopathies.

What the result means

Anaemia is defined by hemoglobin level. WHO cut-offs are most widely used in India: non-pregnant women <12 g/dL, pregnant women <11 g/dL, men <13 g/dL, children 6 months–5 years <11 g/dL. Within anaemia, severity is graded: mild (10–11.9 women, 11–12.9 men), moderate (7–10), severe (<7). Severe anaemia, particularly with symptoms, usually warrants urgent evaluation.

Low hemoglobin is the most common abnormality. Causes seen most often in Indian practice include iron deficiency (most common, driven by limited dietary iron bioavailability in vegetarian diets, menstrual loss, and pregnancy demand), vitamin B12 deficiency (common in vegetarians and the elderly), folate deficiency, thalassaemia trait (genetic, more common in some communities), anaemia of chronic disease (chronic infection like tuberculosis, kidney disease, inflammation), and acute blood loss.

High hemoglobin (above the upper limit) is less common and can reflect dehydration, chronic lung disease, smoking, sleep apnoea, or rarely a primary blood disorder called polycythaemia. Living at high altitude raises hemoglobin physiologically (more red cells to carry less-dense oxygen). Doctors usually look at the other CBC values, hydration status, and possible causes before acting on a raised hemoglobin.

Reference range

Values in g/dL. WHO anaemia cut-offs are the standard reference in India.

Adult men — typical range: Roughly 13.0 – 17.0 g/dL (WHO anaemia cut-off: <13)
Adult non-pregnant women: Roughly 12.0 – 15.0 g/dL (WHO anaemia cut-off: <12)
Pregnant women: WHO anaemia cut-off: <11 g/dL (stricter than non-pregnant)
Children 6 months – 5 years: WHO anaemia cut-off: <11 g/dL
Children 5 – 11 years: WHO anaemia cut-off: <11.5 g/dL
Mild anaemia: Hb 10 – 11.9 g/dL (women) or 11 – 12.9 g/dL (men)
Moderate anaemia: Hb 7 – 10 g/dL
Severe anaemia: Hb below 7 g/dL — usually needs urgent evaluation

Pregnancy uses stricter anaemia cut-offs than non-pregnant adults because the WHO definitions adjust for the natural plasma-volume expansion of pregnancy. Newborns and children use distinct paediatric reference ranges. Altitude raises hemoglobin physiologically — high-altitude communities have higher reference ranges.

Common factors that affect the result

Diet and nutrient status are the dominant drivers of hemoglobin in Indian readers. Iron-deficiency anaemia is the leading single cause — driven by limited dietary iron bioavailability in vegetarian Indian diets (plant-source iron is less absorbable than animal-source iron), menstrual loss, repeated pregnancies, and gut conditions that limit absorption. Vitamin B12 deficiency is widespread in vegetarians; folate deficiency is also common. Combined deficiencies are typical, which is why supplementation is often combined.

Pregnancy lowers hemoglobin on average. Blood plasma volume expands more than red cell mass during pregnancy, diluting hemoglobin. This 'physiological anaemia of pregnancy' is normal up to a point — but Indian women often start pregnancy already iron-deficient, so anaemia in pregnancy is very common and is a focus of antenatal care.

Several conditions falsely raise or lower hemoglobin. Dehydration concentrates blood and raises hemoglobin without more red cells; over-hydration or IV fluid loading does the opposite. Smoking modestly raises hemoglobin (chronic carbon monoxide exposure). Chronic kidney disease lowers it (reduced erythropoietin). Chronic inflammation, infection (notably untreated tuberculosis), and many cancers lower it through 'anaemia of chronic disease'.

When to talk to your doctor

Your hemoglobin is below the WHO anaemia cut-off (men <13, non-pregnant women <12, pregnant women <11), particularly if you have symptoms — tiredness, breathlessness on mild exertion, palpitations, pale skin.
Your hemoglobin has dropped meaningfully from your usual baseline, even if it is still within range — a downward trend matters as much as the absolute value.
You are pregnant and your hemoglobin is below 11 g/dL — pregnancy anaemia needs evaluation and treatment because of effects on both mother and baby.
Iron supplementation is not improving your hemoglobin after 2–3 months — this often points to a different cause (B12/folate deficiency, thalassaemia trait, chronic disease, gut absorption issue) that needs different testing.
Your hemoglobin is well above the upper limit, alongside symptoms like headache, dizziness, or in someone with known lung or sleep-apnoea conditions.

Related tests

Blood Cells

CBC

Hemoglobin