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Electrolytes
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Currently under review
Pending specialist review and validation.
This test measures how much of your hemoglobin is carrying oxygen at the time your blood sample is taken. In the laboratory it is measured by co-oximetry, a method that directly analyzes hemoglobin in a blood sample to determine the fraction bound to oxygen. It is different from a fingertip pulse oximeter because it uses your blood, not a light sensor on the skin.
Co-oximetry can also distinguish normal oxygen-carrying hemoglobin from forms that do not carry oxygen well. The result is reported as a fraction of hemoglobin that is oxygenated and reflects your blood oxygenation at the moment of sampling.
Oxygen saturation helps your care team assess how well your lungs move oxygen into your blood and how effectively oxygen is being delivered to your body. It is commonly ordered when you have breathing problems, chest discomfort, low energy, or when you are receiving oxygen therapy. It is also used around surgery, in emergency care, and in intensive care to guide treatment decisions.
The laboratory method is useful when there may be abnormal hemoglobin or exposures that interfere with oxygen delivery, such as smoke inhalation or certain medicines. By identifying whether oxygen binding is affected, your clinician can decide on next steps, which may include adjusting oxygen, treating an underlying lung or heart condition, or addressing a blood problem.
Your result is interpreted together with the type of sample collected, your symptoms, and other tests such as blood gases and hemoglobin levels. A result that is lower than expected for your situation may suggest a problem with lung function, ventilation, blood flow, or the type of hemoglobin present. Your clinician may respond by checking additional measurements, adjusting oxygen therapy, or investigating causes like infection, asthma or COPD flare, pneumonia, heart issues, or a blood clot.
If your value is unexpectedly low despite adequate oxygen delivery, your team may consider hemoglobin problems or exposures that reduce oxygen binding. Co-oximetry can help by identifying these forms of hemoglobin when ordered as part of a blood gas panel. Trends over time and how you feel are often more informative than a single value, so ask how your result fits with the overall clinical picture.
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.
Arterial samples generally reflect lung oxygenation more directly than venous samples. Values represent a single moment, so rapid changes in breathing or oxygen therapy around the draw can shift the result.
Air bubbles, loose caps, or long delays before analysis can alter dissolved gases and shift oxygen saturation. Proper collection, prompt mixing, and timely analysis help ensure accuracy.
Carboxyhemoglobin and methemoglobin reduce effective oxygen binding. Co-oximetry can detect these, but their presence can lower the reported oxygenated fraction and change interpretation.
Living at higher altitude or receiving supplemental oxygen changes expected saturation. Tell your clinician about recent travel or the oxygen flow you are using at the time of the test.
Fever, hypothermia, acidosis, or alkalosis shift hemoglobin’s affinity for oxygen, which can influence saturation relative to tissue needs. Related blood gas values help put the result in context.
Nitrates, dapsone, local anesthetics, and smoke or carbon monoxide exposure can change hemoglobin and lower effective oxygen delivery. Share recent medications and exposures with your care team.
Low hemoglobin does not necessarily change saturation, but it reduces total oxygen carrying capacity. Your clinician may review hemoglobin and iron studies alongside your saturation.
References