Nocturnal oximetry measures and records the level of oxygen in your blood as you sleep.

What is it?

Nocturnal oximetry is a test to monitor and record the level of oxygen in your blood as you sleep through the night. This test is normally done at home. With this test, an oxygen sensor is placed on your finger and connected to a machine called an oximeter. The oximeter measures and records your heart rate and the level of oxygen carried in your blood.

Why do I need it?

There are several reasons that your healthcare provider may recommend overnight home oximetry. Common reasons include:

  • As part of an initial screening for obstructive sleep apnea (OSA). OSA is a condition in which you briefly stop or reduce your breathing while you sleep. When this happens, the level of oxygen in your blood may drop, which will be measured and recorded on the oximeter.
  • Overnight pulse oximetry monitoring is a cost effective and minimally invasive method for the dentist to adjust your dental device prior to a follow-up home sleep test (HST) or facility-based polysomnography (PSG). While at least one follow-up HST or PSG is usually required, using oximetry reduces the likelihood that you’ll need to return for additional HSTs or PSGs.
  • To assess the need to start, continue, or increase home oxygen for various conditions.

What happens before the test?

Getting the equipment.

The items you need will be provided by your healthcare provider. These include:

  • A wrist-worn oximeter that clips on your finger (this is the machine that records your blood oxygen levels and heart rate).
  • Testing instructions.

Preparing the day of the test.

Unless your healthcare provider gives you special instructions, follow your normal daily routine and take your usual medications.

  • If you take medications or consume alcohol and/or caffeine on the day(s) of your test, write down the times and amounts taken.

Talking with your healthcare provider about home oximetry.

Return the equipment and follow-up with your healthcare provider as advised to get the results and discuss next steps. You may need to have additional sleep testing to confirm a diagnosis of sleep apnea and evaluate treatment.

The table below lists common potential benefits, risks, and alternatives for home oximetry. This list is not exhaustive. Other benefits and risks may apply in your unique medical situation. Talking with your healthcare providers is the most important part of learning about the risks and benefits. If you have questions, be sure to ask.

Potential benefits

Risks and potential problems


  • Can be a first step in screening for OSA.
  • Offers the convenience of being at home.
  • It provides your clinician with objective data which they can use when determining the best treatment settings.
  • If you turn off the oximeter in the night and don’t remember to turn it back on, you won’t have a full night’s results.
  • The test does not provide all the information needed to diagnose sleep apnea or other conditions.
  • If you drop the oximeter (especially into water), it can be damaged.
  • In-lab Polysomnography ("PSG"): An overnight facility based test. A PSG is considered the gold standard for diagnosing apnea and a number of other sleep disorders.
  • Home Sleep Test ("HST"): A multi-channel portable home monitor.
  • Talk to your healthcare provider to determine which option is best for you.