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Arterial Total Hemoglobin (tHb)

Immunology & Autoimmune

Arterial tHbtHbtHb artTotal hemoglobin, arterial

Review status

Currently under review

Pending specialist review and validation.

What it shows

Arterial total hemoglobin, often reported as tHb on a blood gas or co-oximetry panel, measures the amount of hemoglobin present in a sample taken from an artery. It reflects the total pool of hemoglobin in red blood cells, regardless of whether it is carrying oxygen, carbon dioxide, or other molecules. This measurement is performed on arterial blood because it best represents oxygen delivery from the lungs to your tissues.

The result is produced by a co-oximeter, a device that shines light through the blood sample to quantify hemoglobin forms and calculate the total concentration. It is commonly obtained alongside arterial blood gases, oxygen saturation, and related indices during emergency care, surgery, or critical illness.

Why it matters

Hemoglobin is the protein that carries oxygen to your organs. Knowing your arterial total hemoglobin helps clinicians assess if you have enough red blood cell mass to meet your body’s needs, especially during illness, bleeding, or surgery. It supports decisions about treating anemia, evaluating dehydration or overhydration, and considering transfusion when appropriate.

This test is frequently ordered in operating rooms, intensive care units, and emergency departments when rapid decisions are needed. It complements other tests such as a complete blood count, iron studies, or arterial blood gases, helping your care team understand the causes of symptoms like shortness of breath, dizziness, paleness, or fatigue, and to monitor response to therapy.

Understanding your results

Your result is interpreted in the context of your age, sex, medical history, symptoms, and other lab findings. A value lower than expected can occur with anemia, recent blood loss, nutritional deficiencies, chronic disease, or dilution from intravenous fluids. A higher value can be seen with dehydration or conditions that increase red blood cell mass. Trends over time, not just a single value, often provide the clearest picture.

If your result is outside the expected range, your clinician may repeat testing to confirm, review your medications and fluid balance, and order follow-up tests such as a complete blood count, iron and vitamin levels, kidney and thyroid tests, or evaluation for bleeding. Treatment focuses on the underlying cause, which may include nutrition support, managing chronic conditions, adjusting medications, or transfusion when clinically indicated.

Reference ranges

135 – 195 g/L
Female
0 days – 1 day
135 – 195 g/L
Male
0 days – 1 day
0 – 0.02 fraction
All sexes
0 days – 150 years
135 – 185 g/L
Female
1 day – 7 days
135 – 185 g/L
Male
1 day – 7 days
100 – 180 g/L
Female
7 days – 1 month
100 – 180 g/L
Male
7 days – 1 month
95 – 135 g/L
Female
1 month – 6 months
95 – 135 g/L
Male
1 month – 6 months
105 – 135 g/L
Female
6 months – 2 years
105 – 135 g/L
Male
6 months – 2 years
115 – 135 g/L
Female
2 years – 4 years
115 – 135 g/L
Male
2 years – 4 years
115 – 155 g/L
Female
4 years – 10 years
115 – 155 g/L
Male
4 years – 10 years
120 – 160 g/L
Female
10 years – 21 years
130 – 160 g/L
Male
10 years – 21 years
120 – 160 g/L
Female
21 years – 150 years
135 – 175 g/L
Male
21 years – 150 years

Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.

Factors that could impact Arterial Total Hemoglobin (tHb)

  • Sample type and handling

    tHb is typically measured on an arterial blood gas sample. Incorrect sample type, delays to analysis, or improper mixing with heparin can lead to misleading results. Prompt analysis and correct anticoagulant use reduce pre-analytic errors.

  • Intravenous fluids and dilution

    Large volumes of IV fluids given before sampling can dilute circulating red blood cells, lowering the measured hemoglobin. Your care team considers recent fluid administration when interpreting results.

  • Recent bleeding or transfusion

    Active bleeding can lower hemoglobin, while recent red blood cell transfusion can raise it. Very recent transfusions may not be fully equilibrated, so repeat testing may be used to confirm stability.

  • Hydration and diuretics

    Dehydration can concentrate hemoglobin, while overhydration or diuretic use may reduce it. Assessing your fluid status helps explain unexpected results.

  • Altitude, smoking, and chronic lung or heart disease

    Living at higher altitude, smoking, or having chronic lung or heart disease can change hemoglobin levels as your body adapts to oxygen needs. These factors are considered during interpretation.

  • Special populations

    Newborns, children, older adults, and people who are pregnant have different expected ranges and physiology. Age and pregnancy status guide how results are evaluated.

2026

References

  1. McGill University Health Centre. (2015, July 03). tHb Arterial (Task CD 1089327). Laboratory reference ranges.
  2. McGill University Health Centre. (2018, September 24). tHb Arterial (Task CD 1088725). Laboratory reference ranges.
  3. McGill University Health Centre. (2019, January 16). tHb Arterial (Task CD 1088725). Laboratory reference ranges.
  4. McGill University Health Organisation. (2019, May 10). tHb Arterial (Task CD 1088725). Laboratory reference ranges.
  5. International Council for Standardization in Haematology. (2015). ICSH recommendations for hemoglobinometry in human blood. British Journal of Haematology, 170(3), 384-395.
  6. World Health Organization. (2011). Haemoglobin concentrations for the diagnosis of anaemia and assessment of severity. WHO/NMH/NHD/MNM/11.1.