Hemoglobin g/dL to g/L Converter

Hemoglobin in two units: the short answer

To convert hemoglobin from g/dL to g/L, multiply by 10. To convert g/L back to g/dL, divide by 10. A hemoglobin of 13.5 g/dL is therefore 135 g/L, and 118 g/L is 11.8 g/dL. Some laboratories, mainly in parts of Europe, also report hemoglobin in mmol/L: to convert g/dL to mmol/L, multiply by 0.6206; to convert mmol/L to g/dL, multiply by 1.611. A hemoglobin of 14 g/dL is about 8.7 mmol/L. The converter above handles g/dL ↔ g/L and shows the World Health Organization's anaemia thresholds and typical adult ranges.

Hemoglobin is part of the full blood count, probably the most frequently ordered blood test in the world. The g/dL-to-g/L conversion is simple, but mistakes still happen – a value of "12" can be read as g/dL (borderline) when it was actually mmol/L (very high) – and the thresholds for anaemia vary by age, sex, pregnancy and altitude. This guide explains the units, the thresholds and how to read a hemoglobin result in context.

What hemoglobin is

Hemoglobin (haemoglobin in British English) is the iron-containing protein inside red blood cells that carries oxygen from the lungs to the tissues and helps carry carbon dioxide back. Each hemoglobin molecule has four protein chains (two alpha and two beta in normal adult hemoglobin A), each holding a heme group with an iron atom that binds one oxygen molecule.

The hemoglobin concentration in the blood depends on:

• how many red cells the bone marrow produces (which needs iron, vitamin B12, folate and the kidney hormone erythropoietin)
• how long red cells survive (normally about 120 days)
• how much blood is lost
• the volume of plasma in which the red cells are suspended

A low hemoglobin is called anaemia (anemia in US English); a high hemoglobin is called erythrocytosis or polycythaemia.

g/dL, g/L and mmol/L explained

• g/dL (grams per deciliter) – used in the United States and many other countries.
• g/L (grams per liter) – used in the UK, Canada, Australia, much of Europe and in WHO documents since 2024. It is the same measurement, with the decimal point moved one place.
• mmol/L – used in the Netherlands and some other countries. It is based on the molar mass of a single heme-carrying subunit (about 16,114 g/mol), which is why the factor is 0.6206.

Some older reports used g/100 mL, which is identical to g/dL.

Why the factors are 10 and 0.6206

A deciliter is one-tenth of a liter, so a concentration in g/L is 10 times the concentration in g/dL. For mmol/L, 1 g/dL is 10 g/L, and 10 ÷ 16.114 = 0.6206 mmol/L, counting each hemoglobin monomer as one unit.

How to convert hemoglobin step by step

1. Identify the unit. Values around 12–17 are usually g/dL; values around 120–170 are g/L; values around 7.5–11 are usually mmol/L.
2. g/dL to g/L: multiply by 10.
3. g/L to g/dL: divide by 10.
4. g/dL to mmol/L: multiply by 0.6206.
5. mmol/L to g/dL: multiply by 1.611.

Worked examples

• 7.0 g/dL = 70 g/L = 4.3 mmol/L – a common threshold for blood transfusion in stable adults.
• 11.0 g/dL = 110 g/L = 6.8 mmol/L – the WHO threshold for anaemia in pregnancy.
• 12.0 g/dL = 120 g/L = 7.4 mmol/L – the WHO threshold for anaemia in non-pregnant women.
• 13.0 g/dL = 130 g/L = 8.1 mmol/L – the WHO threshold for anaemia in men.
• 16.5 g/dL = 165 g/L = 10.2 mmol/L – a level used in the diagnostic criteria for polycythaemia vera in men.
• 9.0 mmol/L × 1.611 = 14.5 g/dL = 145 g/L.

Hemoglobin conversion chart

Hemoglobin ranges and anaemia thresholds

WHO anaemia thresholds

The World Health Organization's 2024 guideline sets the following hemoglobin thresholds for anaemia at sea level (values below these indicate anaemia):

WHO further grades anaemia by severity; in non-pregnant adult women, for example, mild anaemia is 110–119 g/L, moderate 80–109 g/L and severe below 80 g/L. In men, mild is 110–129 g/L.

Typical laboratory ranges

Laboratory reference ranges are often slightly different from WHO thresholds. Typical adult ranges are about 13.0–17.0 g/dL (130–170 g/L) for men and 12.0–15.5 g/dL (120–155 g/L) for women. Some laboratories use lower limits of 13.5 g/dL for men and 11.5 g/dL for women. Newborns have much higher hemoglobin (often 14–22 g/dL) that falls over the first two to three months.

Altitude and smoking

People living at high altitude have higher hemoglobin as an adaptation to lower oxygen, and WHO recommends adjusting thresholds upwards above 500 meters elevation. Smokers also have higher hemoglobin because carbon monoxide reduces oxygen delivery; WHO suggests an adjustment of about 3–7 g/L depending on how much a person smokes.

Reading hemoglobin in context: the red cell indices

A full blood count reports more than hemoglobin. The red cell indices help identify the cause of anaemia:

• MCV (mean corpuscular volume) – average red cell size. Low MCV (microcytic) suggests iron deficiency or thalassaemia trait; high MCV (macrocytic) suggests B12 or folate deficiency, alcohol, liver disease, hypothyroidism or some medicines; normal MCV (normocytic) suggests anaemia of chronic disease, kidney disease, acute blood loss or mixed causes.
• MCH and MCHC – the amount and concentration of hemoglobin per cell; low in iron deficiency.
• RDW (red cell distribution width) – variation in size; often raised early in iron deficiency.
• Reticulocyte count – young red cells; high when the marrow is responding to blood loss or haemolysis, low when production is impaired.
• Hematocrit (packed cell volume) – the proportion of blood volume taken up by red cells, roughly three times the hemoglobin in g/dL (for example 14 g/dL ≈ 42%).

Causes of anaemia

• Iron deficiency – the most common cause worldwide, from blood loss (heavy periods, gut bleeding), poor intake, increased needs (pregnancy) or malabsorption.
• Anaemia of inflammation (chronic disease) – in chronic infections, autoimmune disease, cancer and kidney disease.
• Vitamin B12 or folate deficiency.
• Chronic kidney disease – reduced erythropoietin.
• Haemolysis – early destruction of red cells, from inherited conditions (sickle cell disease, thalassaemia, G6PD deficiency, hereditary spherocytosis) or acquired causes (autoimmune haemolysis, some medicines).
• Bone marrow disorders – aplastic anaemia, myelodysplasia, leukaemia, marrow infiltration.
• Acute blood loss – hemoglobin may not fall until fluids have redistributed, hours after the bleed.

High hemoglobin

A high hemoglobin can be:

• Relative – due to reduced plasma volume, for example dehydration or diuretics.
• Secondary – a response to low oxygen or increased erythropoietin: smoking, chronic lung disease, sleep apnoea, high altitude, some kidney tumours and cysts, and testosterone therapy (a common cause in men).
• Primary – polycythaemia vera, a bone marrow disorder usually caused by a JAK2 mutation. WHO diagnostic criteria include a hemoglobin above 16.5 g/dL (165 g/L) in men or 16.0 g/dL (160 g/L) in women, or a raised hematocrit.

High hemoglobin increases blood viscosity and the risk of blood clots, particularly in polycythaemia vera.

Symptoms of anaemia

Symptoms depend on how low the hemoglobin is and how quickly it fell. A slow fall over months allows the body to adapt, and some people feel well with a hemoglobin of 9–10 g/dL (90–100 g/L). A rapid fall from bleeding causes symptoms at higher levels. Common symptoms include:

• tiredness, reduced exercise tolerance and weakness
• breathlessness on exertion
• palpitations or a fast heartbeat
• headaches, dizziness and difficulty concentrating
• pale skin, inner eyelids or nail beds
• cold hands and feet
• worsening angina in people with heart disease

Iron deficiency may also cause brittle or spoon-shaped nails, hair loss, a sore tongue, cracks at the corners of the mouth, restless legs and cravings for ice or non-food substances (pica).

Transfusion thresholds

Blood transfusion decisions in hospital are guided partly by hemoglobin. The 2023 AABB international guidelines recommend a restrictive strategy for most stable hospitalised adults, considering transfusion when hemoglobin falls below 7 g/dL (70 g/L). Higher thresholds are suggested for some groups – for example 7.5 g/dL (75 g/L) for people undergoing cardiac surgery and 8 g/dL (80 g/L) for those having orthopaedic surgery or with pre-existing cardiovascular disease. Symptoms, ongoing bleeding and the overall clinical picture also matter, and a single number never decides alone. Because UK guidance is written in g/L and US guidance traditionally in g/dL, these thresholds are a common place where unit confusion must be avoided.

Anaemia in chronic kidney disease

In chronic kidney disease, reduced production of erythropoietin by the kidneys causes anaemia, which becomes more common as eGFR falls. Treatment includes correcting iron deficiency (often with intravenous iron) and, when needed, erythropoiesis-stimulating agents (ESAs) such as epoetin or darbepoetin. Trials found that aiming for a normal hemoglobin with ESAs increased the risk of stroke and other complications, so guidelines recommend avoiding high targets; KDIGO suggests generally not using ESAs to intentionally raise hemoglobin above 11.5 g/dL (115 g/L) in adults, and NICE recommends an aspirational range of 100–120 g/L for most adults.

Hemoglobin and blood donation

Blood services check hemoglobin before each donation to protect donors. Minimum levels differ between countries; for example, many services require at least 12.5 g/dL (125 g/L) for women and 13.0–13.5 g/dL (130–135 g/L) for men, using a finger-prick or venous test. Regular donors can become iron deficient, and some blood services now measure ferritin and adjust donation intervals accordingly.

Hemoglobin versus HbA1c

Despite the similar name, HbA1c (glycated hemoglobin) is a different test: it measures the percentage of hemoglobin that has glucose attached, reflecting average blood sugar over two to three months. It is reported in % or mmol/mol, not in g/dL or g/L. Anaemia and hemoglobin variants can affect HbA1c accuracy, which is one reason clinicians look at both results together. To interpret an HbA1c result, use our A1C calculator and chart.

What affects hemoglobin results

• Hydration – dehydration raises hemoglobin; fluid overload and pregnancy dilute it.
• Posture and tourniquet time – standing and prolonged tourniquet use raise values slightly.
• Recent blood donation or transfusion.
• Altitude and smoking.
• Endurance training – athletes often have slightly lower hemoglobin due to an expanded plasma volume ("sports anaemia"), which is a normal adaptation.
• Sample type – finger-prick and point-of-care devices can differ from laboratory analysers by around 0.5–1 g/dL.
• Lipaemia or very high white cell counts can falsely raise automated hemoglobin results.

Hemoglobin variants and thalassaemia

Not all hemoglobin is the standard adult form. Inherited changes in the globin chains cause hemoglobin variants, such as hemoglobin S (sickle cell), hemoglobin C and hemoglobin E, and reduced production of chains causes thalassaemias. Carriers of thalassaemia (thalassaemia trait) often have a mildly low hemoglobin with very small red cells (low MCV) and a normal or high red cell count – a pattern easily mistaken for iron deficiency. Giving iron to someone with thalassaemia trait and normal iron stores does not help and can be harmful over time, so ferritin is checked before treating a microcytic anaemia, and hemoglobin electrophoresis or HPLC is used to identify variants. Many countries offer antenatal screening for these conditions.

Comparing hemoglobin results across countries

Because g/dL and g/L differ by exactly a factor of ten, conversion is easy – but the thresholds attached to results can differ. A woman whose UK report shows 118 g/L flagged as low and whose US report shows 11.9 g/dL flagged as normal might think the reports disagree. In fact the values are almost identical (118 g/L = 11.8 g/dL); the difference lies in each laboratory's lower limit (for example 120 g/L in one and 11.6 g/dL in the other). WHO thresholds offer a consistent reference for comparison.

When to see a doctor

See a doctor if your hemoglobin is below the threshold for your age and sex, especially with tiredness, breathlessness, palpitations, pale skin, or if you have heavy periods, black or bloody stools, or unexplained weight loss. In men and postmenopausal women, unexplained iron-deficiency anaemia should be investigated for possible gut bleeding. Seek urgent care for a hemoglobin below about 7 g/dL (70 g/L), chest pain, fainting or severe breathlessness. A persistently high hemoglobin, particularly with headaches, itching after bathing or a history of blood clots, also warrants assessment.