Normal Po2 Levels-what Your ABG Results Are Trying To Say

Your normal arterial PO2 (PaO2) is typically 75-100 mmHg on a room-air arterial blood gas (ABG) test, though reference ranges can vary by lab, altitude, age, and how the sample was collected.

In clinical terms, "PO2 levels" usually means PaO2-the partial pressure of oxygen dissolved in arterial blood-so the number is most useful when interpreted alongside your oxygen support status (room air vs. supplemental oxygen) and other ABG values like saturation (SaO2) and CO2.

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Historically, standard ABG interpretation has used fixed "normal ranges" (like 75-100 mmHg) because they map to typical adult oxygenation physiology at sea level, but clinicians increasingly emphasize context (oxygen fraction, ventilation status, and clinical setting) rather than treating the number as a standalone grade.

What "PO2" usually means

When people ask "normal PO2 levels," they most often mean PaO2 measured from an arterial blood sample, not venous PO2.

An ABG report may show multiple oxygen-related outputs-PaO2 (partial pressure), SaO2 (oxygen saturation), and sometimes FiO2-related calculations-which is why two patients can both have "normal PO2" ranges yet still differ clinically.

Normal PO2 ranges (adults)

For adults breathing room air at sea level, common reference ranges place PaO2 around 75-100 mmHg (often shown as ~10.5-13.5 kPa in some reporting systems).

Many clinical summaries also describe broad bands for severity of hypoxemia (low oxygen), which is how the same number becomes "normal" in one setting and "concerning" in another.

• Normal (room air): 75-100 mmHg
• Mild hypoxemia (context-dependent): 60-74 mmHg
• Moderate hypoxemia (context-dependent): 40-59 mmHg
• Severe hypoxemia: < 40 mmHg
• Oxygen saturation often pairs with this: SaO2 commonly 94-100% in "normal" references

ABG values that travel together

PaO2 is not interpreted in isolation; oxygen levels (PO2/PaO2) are typically read alongside pH, PaCO2, and bicarbonate to understand whether a breathing problem, acid-base problem, or oxygenation problem is driving symptoms.

If your ABG report says pH 7.35-7.45 and PaCO2 4.7-6.5 kPa (about 35-45 mmHg), the oxygen result (PaO2) becomes easier to contextualize because the ventilation pattern is more apparent.

ABG metric	Typical "normal" adult range	What it usually reflects
PaO2 (PO2)	75-100 mmHg (≈10.5-13.5 kPa)	Oxygen pressure in arterial blood
SaO2	94-100%	Oxygen saturation on hemoglobin
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