Should you buy a pulse oximeter?

What are pulse oximeters, and how does the body use oxygen?

Pulse oximeters measure the oxygen in your blood. You breathe oxygen into your lungs, where it’s loaded into red blood cells. Red blood cells are full of a protein called hemoglobin, which is where the oxygen is stored. When they’re pumped around your body, red blood cells deliver oxygen to your organs and muscles. Your body uses up oxygen, and makes carbon dioxide, to generate energy. 

How do we measure oxygen in the body?

Pulse oximeters measure “oxygen saturation,” which is the percentage of hemoglobin proteins storing oxygen. In arteries, oxygen saturation for healthy people is usually between 95% and 100%. Saturation below 90% is usually considered worrisome. Some people who get very sick with COVID experience a decrease in their oxygen saturation well below 90%, and they might need supplemental oxygen or even a ventilator.

Should you buy a pulse oximeter? 

Here are a few reasons why it’s not cut and dried. First, the pulse oximeters that are available online are not standardized and generally not very accurate. Second, even high-quality oximeters are a bit finicky because readings are influenced by room and skin temperature, skin pigmentation, ambient lighting, the presence of nail polish, and the snugness of the meter's contact with the skin. Third, even healthy people, oxygen saturation likely fluctuates based on their recent activity, non-COVID illnesses, and other factors. 

All that said, there are some circumstances when using a pulse oximeter would make sense. If you have an existing lung condition and already monitor your oxygen saturation, continuing to do so might help detect subtle but serious changes if you get sick with COVID. And even if you don’t have lung problems, if you get moderately sick with COVID, your doctor might recommend monitoring your oxygen saturation at home to decide whether and when you need to go to the hospital. 

So if you have a pulse oximeter, keep it. But if you don’t, speak with your doctor before rushing out to buy one.

Last update: Month Day, Year, HH:MM pm ET

Science review: ERS, GSN