What to Check Before Buying a Pulse Oximeter

Overnight oximeters look alike in the photos. The differences that matter are in the small print.

Here are seven things to check before you pay.

Is it made for overnight use?

Some oximeters only take a spot reading. Check the listing says it records continuously while you sleep.

• A spring clip is for spot checks. See do cheap pulse oximeters work overnight?.
• A smartwatch usually gives you a nightly summary, not the full recording. See smartwatch SpO2 vs a pulse oximeter.

Can you export your data?

This is the big one. Look for CSV export, or at least a file you can save and open elsewhere.

• With an export, your nights are yours. You can open them in a spreadsheet, send them to your doctor, or load them into another tool.
• Without one, you're stuck with one app for as long as it exists.

Here's what an O2Ring CSV export looks like, and how to move your history out of ViHealth.

Does it store the night on the device?

Onboard memory means the device records by itself and syncs in the morning. Without it, your phone has to stay connected and awake all night.

Check how many nights it holds. If you sync every morning, a few is plenty. If you travel without your phone nearby, count the nights you'll be away.

Will the battery last?

It needs to cover your longest night with recording on. Check two figures on the listing:

• Hours of use per charge.
• How long a full charge takes.

A device that needs charging every day is fine, as long as you'll remember to do it.

What do those figures look like in practice?

Here's what Wellue's own listings said for its three overnight models at the time of writing. Specs change between versions, so check the listing for the one you're buying.

Each session holds up to 10 hours.

So with any of these, sync at least every fourth morning. The battery is the bigger difference: one model runs several nights, the other two need charging every day or two.

Can you sleep in it?

You won't keep wearing something that wakes you up.

• A ring has no cable but has to fit snugly. See O2Ring sizing.
• A wrist unit has an adjustable finger sensor on a short cable. See SleepU tips and Checkme O2 Max tips.

More on each in ring vs fingertip vs wrist. Also check the returns policy, in case it doesn't suit you.

Is the app still supported?

Open the app's store page before you buy the hardware.

• Has it been updated in the last few months?
• Does it run on your phone?
• Do recent reviews mention sync problems?

Then check what else can read the device. If other tools can sync with it or import its files, you're not relying on one app. We list some in ViHealth alternatives.

Does it have an alert, and do you want one?

Some overnight oximeters vibrate when your SpO2 drops below a level you set.

• Check you can change the level and the strength.
• Check you can turn it off. A buzz that wakes you changes the night you're recording.

It's a nudge, not an alarm to rely on. See the O2Ring vibration alert.

What about accuracy claims?

Most listings quote a similar figure, so it won't help you choose. Wellue's SleepU listing, for example, says plus or minus 2% between 80% and 99%.

Two things are worth knowing:

• Many consumer oximeters are sold for general wellness, not medical use. Check what the listing says the device is intended for.
• The FDA lists things that affect any oximeter: poor circulation, skin pigmentation, skin thickness, skin temperature, tobacco use and nail polish.

How you wear it matters more than the number on the box. See why a reading might be wrong and pulse oximeters and skin tone.

What should it cost?

At the time of writing, Wellue's own store listed its three overnight models between about $150 and $230, depending on the model and the discount. Check the listing, because prices change.

Before you compare prices, check:

• Is the app free, or is there a subscription?
• Is the charging cable included?
• How long is the warranty?

What's the quick checklist?

• Records all night, not spot checks
• CSV or file export
• Records to onboard memory
• Battery covers a full night
• Comfortable enough to forget
• App updated recently
• Alert you can adjust or turn off

We compared the three Wellue models in O2Ring vs Checkme O2 Max vs SleepU. PulseOxTracker syncs with all three and imports their CSV files, so you can compare weeks.

Still deciding whether to buy at all? Read is an overnight pulse oximeter worth it?.

A home oximeter is not a sleep study. If you snore loudly, stop breathing or gasp in your sleep, or you're exhausted during the day, see a doctor.

Not a medical device. Does not diagnose, treat or prevent any condition. Discuss results and changes with a clinician.

References

1. US Food and Drug Administration. Pulse Oximeters, including a summary of the February 2021 safety communication. fda.gov. Checked October 2026.
2. Wellue. O2Ring product listing. getwellue.com. Checked October 2026.
3. Wellue. SleepU product listing. getwellue.com. Checked October 2026.
4. Wellue. Checkme O2 Max product listing. getwellue.com. Checked October 2026.