What a pulse oximeter can—and cannot—tell you
An estimated oxygen reading needs context.
A pulse oximeter estimates blood oxygen saturation. The FDA identifies several influences on accuracy, including circulation, skin pigmentation, skin temperature and nail polish. A number on a screen is not a complete assessment of how someone is doing.
Follow the instructions for the exact device and discuss monitoring with your clinician. If you feel unwell or have concerning symptoms, seek appropriate medical help even if the displayed number seems reassuring. Compare intended use and labeling before buying; a wellness product is not automatically suitable for medical decisions.