Pulse Oximeters Are Less Accurate on Darker Skin—And There's No Good Alternative

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Pulse oximeters are widely used to measure blood oxygen levels, but these devices may be less reliable for people with darker skin tones, potentially leading to delayed medical care.

Normal readings range from 95% and 100%, and anything below 88% requires immediate medical attention. A 2020 study found that Black patients were three times more likely than White patients to experience undetected low blood oxygen levels, known as occult hypoxemia.

This issue has been recognized since the 1990s, but the pandemic brought more attention to it, as pulse oximeters were used to guide COVID-19 treatment plans. The Food and Drug Administration (FDA) has acknowledged the inaccuracy of these devices and now plans to release a new draft guidance for pulse oximeter manufacturers by 2025.

“We’re depending on these devices. We’re using them all the time, and we are making decisions based entirely on that number,” said Thomas Valley, MD, MSc, an associate professor of pulmonary and critical care medicine at the University of Michigan who conducted research on the racial bias of pulse oximeters.

When you breathe, oxygen enters your lungs and travels through your bloodstream to your heart and the rest of your body. Conditions like lung disease, heart failure, and COVID-19 can cause low blood oxygen levels.

Pulse oximeters clip onto your fingertip and measure blood oxygen levels using a light that passes through your skin and blood. A sensor on the other side captures the light and calculates oxygen saturation based on the amount of light that wasn’t absorbed.

Most pulse oximeters used in the United States today are based on a design developed in Japan in the 1970s. This original pulse oximeter was only tested on people with lighter skin, according to a report by Johns Hopkins University.“Each company created their proprietary algorithm or formula to take that light number and spit it out into a percent of oxygen,” Valley said. “Because this device wasn’t tested broadly, that calibration is off for individuals with darker skin tone.”

Some pulse oximeter manufacturers say their devices work accurately on all skin tones. A recent industry-funded study found that Masimo RD SET pulse oximeters were accurate for both Black and White volunteers. However, Valley said pulse oximeter tests need to focus on sick patients, not healthy volunteers.

“We recognize that there is more work to be done and have been making proactive efforts both to continue refining and improving our technology and to advocate for improvements industrywide. We have been working with the FDA, global regulators, standards organizations, and industry groups to drive improvements in the standards for pulse oximeters,” a Masimo spokesperson told Verywell in an email.

Pulse oximetry is a painless test to measure lung function, but dark skin pigmentation isn’t the only factor that can affect accuracy. Dark nail polish, artificial nails, skin temperature, skin thickness, and tobacco use can also impact results.

Randy Gould, DO, a cardiologist at Manhattan Cardiology, explained that when he suspected a pulse oximeter gave an inaccurate reading, he would switch fingers, alternate hands, or even test it on himself. If the issue persisted, he would try using a completely different pulse oximeter.

Unfortunately, there aren’t that many alternatives to pulse oximeters for measuring blood oxygen levels. One available option is an invasive arterial blood gas test that requires a blood sample from an artery, which is more uncomfortable than a standard blood test using a vein.

“That means our African American patients have the burden of being worried that their clinicians may be being falsely reassured by a normal reading or advocating for one of those painful arterial blood gas punctures, and that seems like a bad choice,” said Theodore J. Iwashyna, MD, PhD, a Bloomberg Distinguished Professor of Social Science and Justice in Medicine at Johns Hopkins University.

Regulatory changes could help ensure that pulse oximeters provide accurate results for all patients. Current FDA guidance from 2013 recommends testing on healthy individuals and states that device testing must include “at least two darkly pigmented subjects” or 15% of the sample pool, whichever is larger.

Iwashyna said this testing method excludes patients who have urgent medical needs, especially in the ICU. “We have predominantly older patients, often who have cardiovascular disease, and I want to know in that patient in my ICU is it working,” he added.

The FDA says it is working on updating the draft guidance, though it’s unclear what specific changes will be made. Two pulse oximeter manufacturers—Zacurate and Nonin—did not respond to Verywell’s request for comment on how they plan to improve their devices for more accurate readings.

Valley said he hopes that the new FDA guidance will include plans for post-market evaluations to assess how well the devices perform in real-world conditions, but the real solution is developing a pulse oximeter that works reliably for everyone.

Researchers across the country—including at Brown University and the University of Texas at Arlington—have started working on improving pulse oximeter technology for people with dark skin.

“There are some ideas out there that might be promising in terms of using different wavelengths,” Valley said. “I think there are technological solutions out there, they just haven’t made it to a pulse oximeter that is widely used.”

If you rely on a pulse oximeter to monitor your oxygen levels, the device may give less accurate readings, especially if you have darker skin. Discuss any concerns with your healthcare provider, and consider asking for additional tests if your symptoms do not match the pulse oximeter reading.

National Library of Medicine: MedlinePlus. Pulse oximetry.

Sjoding MW, Dickson RP, Iwashyna TJ, Gay SE, Valley TS. Racial bias in pulse oximetry measurement. N Engl J Med. 2020;383(25):2477-2478. doi:10.1056/NEJMc2029240

Jubran A, Tobin MJ. Reliability of pulse oximetry in titrating supplemental oxygen therapy in ventilator-dependent patients. Chest. 1990;97(6):1420-1425. doi:10.1378/chest.97.6.1420

Johns Hopkins Bloomberg School of Public Health. The problem with pulse oximeters: a long history of racial bias.

Yale Medicine. Pulse oximetry.

Sharma V, Barker SJ, Sorci R, Park L, Wilson WC. Racial effects on Masimo pulse oximetry: impact of low perfusion index. J Clin Monit Comput. 2024;38(2):347-354. doi:10.1007/s10877-023-01113-2

National Library of Medicine: MedlinePlus. Arterial blood gas (ABG) test.

Brown University. Correcting bias in pulse oximeters.

Gokhale SG, Daggubati V, Alexandrakis G. Innovative technology to eliminate the racial bias in non-invasive, point-of-care (Poc) haemoglobin and pulse oximetry measurements. BMJ Innov. 2023;9(2):73-77. doi:10.1136/bmjinnov-2022-001018

By Stephanie BrownBrown is a nutrition writer who received her Didactic Program in Dietetics certification from the University of Tennessee at Knoxville. Previously, she worked as a nutrition educator and culinary instructor in New York City.