> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sonohealth.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Pulse Oximeter Accuracy: Skin Tone, Nail Polish, and Motion

> What affects pulse oximeter accuracy — skin pigmentation, nail polish, cold hands, motion, and poor circulation — and how to get the most reliable reading at home.

Fingertip pulse oximeters are convenient and useful, but several factors can throw off a reading. Knowing them helps you interpret your numbers correctly and avoid false reassurance.

## How does a pulse oximeter work?

A pulse oximeter shines light through your fingertip and estimates oxygen saturation (SpO2) from how the blood absorbs it. Because it relies on light passing through tissue and detecting a pulse, anything that interferes with light or blood flow can affect the reading. See [normal oxygen levels](/pulse-oximeter/normal-oxygen-levels) for healthy ranges.

## Does skin tone affect accuracy?

Yes — this is important. Research has shown that fingertip pulse oximeters can **overestimate** oxygen levels in people with darker skin, sometimes missing genuinely low oxygen (called occult hypoxemia). If you have darker skin, treat readings as a trend rather than an exact value, watch your symptoms regardless of the number, and tell your doctor if you feel worse even when the reading looks normal.

## Can nail polish or cold hands change the reading?

Yes. Dark **nail polish**, artificial nails, **cold hands**, and poor circulation can all lower or destabilize a reading by interfering with light or blood flow. For the most reliable result: remove polish, warm your hands, and use a finger with good circulation.

## Why does motion matter?

Movement and shivering create "motion artifact" that confuses the sensor. Sit still, rest your hand on a table, and wait for the number to **stabilize** for several seconds before trusting it. A jumping or fluctuating reading usually means you need to hold steady, not that your oxygen is unstable.

## How do I get the most accurate reading?

* Warm, still hand resting on a flat surface
* No nail polish or artificial nail on the test finger
* Wait for the value to settle for 10–15 seconds
* Take a few readings and look at the consistent value
* Note the [pulse-rate number](/pulse-oximeter/normal-oxygen-levels) too, which should match a manual pulse check

## When should a reading prompt action?

Trust symptoms over a single number. Breathlessness, confusion, bluish lips, or chest pain warrant urgent attention **regardless** of the SpO2 shown. People with [COPD or asthma](/pulse-oximeter/copd-asthma-monitoring) should follow the personal targets their doctor sets.

<Warning>
  A home pulse oximeter is a screening aid, not a diagnostic device, and it can read falsely normal — especially with darker skin. Seek medical care for breathing difficulty or other concerning symptoms even if your reading looks fine.
</Warning>

**Related:** [Normal Oxygen Levels](/pulse-oximeter/normal-oxygen-levels) · [COPD & Asthma Monitoring](/pulse-oximeter/copd-asthma-monitoring) · [Overview](/pulse-oximeter/overview)