Acrylic nails can interfere with pulse oximetry, but the effect depends on the pulse oximeter model, whether the acrylics are polished, and the color of any polish applied. Unpolished acrylic nails alone appear to have minimal impact on readings, while dark-colored polish over acrylics can lower oxygen saturation readings by a clinically meaningful amount.
How Pulse Oximeters Read Through Your Nail
A pulse oximeter works by shining two wavelengths of light through your fingertip: red light at 660 nm and infrared light at 940 nm. A sensor on the other side of your finger detects how much light passes through. Because oxygen-rich blood and oxygen-poor blood absorb these wavelengths differently, the device calculates your blood oxygen level (SpO2) based on the ratio of light absorbed.
Anything sitting between the light source and the sensor can absorb, scatter, or block some of that light. Acrylic material adds an extra layer on top of your natural nail, and if that layer is tinted or covered in dark polish, it changes how much red and infrared light reaches the sensor. The device then has less signal to work with, or receives a distorted ratio, which can skew the reading.
What the Research Shows
A study comparing SpO2 readings before and after acrylic nail application found that unpolished acrylics had no statistically significant effect. The mean reading was 97.33% on bare nails and 97.58% with acrylics applied, a difference well within normal variation. So if your acrylics are clear or unpainted, you likely don’t need to worry.
The picture changes when polish enters the equation. A separate study found that black, blue, and green nail polish significantly lowered oximeter readings. Blue and green caused larger drops than purple and red, with black producing an intermediate decrease. These findings apply whether the polish is on natural nails or over acrylics. The darker the color, the more light it absorbs before it can reach the sensor.
One clinical study that tested acrylic nails specifically found a bias of negative 1.1% in SpO2 with one oximeter model, a statistically significant error, while a different oximeter showed a smaller, non-significant shift of positive 0.8%. This means the degree of interference partly depends on the device being used. The researchers concluded that acrylic nails “may impair the measurement of oxygen saturation depending on the pulse oximeter used and may cause significant inaccuracy.”
When a Small Error Matters
For a healthy person checking their oxygen at home, a 1% difference in SpO2 is unlikely to change anything meaningful. Normal oxygen saturation runs between 95% and 100%, and most people hover around 97% to 99%. A reading of 96% instead of 97% won’t trigger concern.
But in clinical settings, that margin matters more. If someone has pneumonia, heart failure, or is under anesthesia, clinicians use SpO2 to make real-time decisions about oxygen delivery. A 1% to 2% underestimate could mask a genuine drop below 90%, the threshold where oxygen levels become dangerously low. In those situations, even a small systematic error from nail coverings can lead to delayed treatment.
How to Get an Accurate Reading With Acrylics
If you need a pulse oximeter reading and have acrylic nails, you have several practical options.
- Use a bare finger. If even one nail is free of acrylics or dark polish, use that finger. Clear or very light polish is least likely to interfere.
- Turn the sensor sideways. Placing the oximeter clip sideways on your finger so the light passes through the fleshy sides rather than through the nail bypasses the acrylic entirely. The study that tested this approach used it as a reference technique to compare against readings taken through acrylics.
- Try the earlobe. Ear clip sensors avoid your nails altogether. Research on alternative sensor sites shows that ear oximetry is reliable and, in patients with low oxygen levels, can actually be more accurate than finger placement.
- Use a toe. If you don’t have polish on your toenails, a toe sensor works, though toe readings tend to slightly underestimate oxygen saturation compared to finger readings.
Removing one acrylic nail is the most straightforward fix if accuracy is critical, such as before surgery or during a hospital stay. Many hospitals will ask you to remove at least one artificial nail for this reason.
Dark Polish Is the Bigger Problem
It’s worth separating two issues that often get lumped together. The acrylic material itself, when clear and unpolished, causes little to no interference in most studies. The real culprit is dark-colored polish, particularly blue, black, and green shades. These colors absorb light in the same wavelength range the oximeter uses, which tricks the device into calculating a lower oxygen level than what’s actually in your blood.
If you wear acrylics with a French manicure or nude colors, you’re far less likely to see distorted readings than someone wearing navy or black gel polish. Red polish can also interfere, but generally produces a smaller error than darker shades.
The FDA still lists nail polish as a recognized factor that can affect pulse oximeter accuracy. Modern devices use more sophisticated signal processing than older models, including techniques to filter out interference from static absorbers, but no current algorithm fully compensates for opaque nail coverings that block or distort the light signal.