When to get help

Should I check my blood oxygen when I'm sick?

By GyroscopeUpdated November 15, 20266 sources

Yes, if you have a finger oximeter, it’s a useful second check while you’re sick, as long as how you feel comes first. Sit still with a warm hand, wait for a steady number and write it down with the time. Call your doctor at 92 or lower, and get medical care now at 88 or lower.

Lots of people bought a pulse oximeter during COVID and it’s been in a drawer since. Then a cold or the flu turns into a cough, and out it comes. The worry is usually one of two things. Either the number looks fine and you wonder if you can ignore how bad you feel, or it shows 94 and you wonder if that’s an emergency.

What number should worry me?

MedlinePlus, the US National Library of Medicine’s health site, gives the lines for a home oximeter. A normal oxygen level is 95 to 100. Contact your doctor at 92 or lower. At 88 or lower, get medical care right away.

A 93 or 94 sits just under the normal range. Warm your hands, sit still for a few minutes and check again. If it stays there and you feel worse, call your doctor and tell them the numbers you’ve written down.

If you have a lung disease such as COPD, or pneumonia, MedlinePlus says your levels can be somewhat lower and still acceptable, so the target your own doctor gives you is the one to follow. If you live up high, your number can sit a little lower too.

How do I take a number I can trust?

The FDA gives four steps for a home oximeter. Make sure your hand is warm, relaxed and held below the level of your heart. Take off any nail polish on that finger. Sit still and keep that hand still. Then wait a few seconds until the number stops changing and shows one steady number.

Then write down the number with the date and time, the FDA says, so you can see any change. One number is a snapshot. Four or five over two days show whether you’re getting better or worse, and that’s what your doctor will want to hear.

How do I measure my blood oxygen correctly? has the details, and every number from 85 to 100 shows what yours means.

Can the number look fine when I’m not?

Yes, and that’s why symptoms win. The FDA says some people with low oxygen have no symptoms, and it also says to call your doctor for bluish color in your face, lips or nails, shortness of breath or a cough that’s getting worse, restlessness, chest pain or tightness, or a racing pulse.

Oximeters also tend to show too high when oxygen is low, and more so on darker skin. In hospital patients whose finger oximeter showed 92 to 96, a blood test found true oxygen under 88 for 11.7% of Black patients’ measurements and 3.6% of White patients’. If your skin is darker and your oximeter shows 88 to 95, lean on how you feel even more, and tell your doctor the number with that in mind.

Cold skin, poor circulation, dark nail polish, artificial nails and tobacco use can all push the number off too, MedlinePlus says.

Can I use my watch instead?

For this, a finger clip is the better tool. In 9 healthy young adults breathing low-oxygen air in a lab, an Apple Watch Series 7 was off by about 5.8 points once true oxygen fell under 88, and a medical finger oximeter by about 3.5. Apple says its Blood Oxygen measurements aren’t meant for medical use.

A watch is fine for spotting your nights changing over weeks. When you’re sick and the question is whether to call someone today, take the number from your finger and listen to your body. Not every drugstore clip is checked either. The FDA says oximeters sold for general wellness or sports aren’t reviewed by the agency before they go on sale.

When is it an emergency?

The CDC’s emergency signs don’t depend on any number. Call 911 for trouble breathing, chest pain or pressure that doesn’t go away, new confusion, being unable to wake or stay awake, or lips, nail beds or skin that look pale, gray or blue. When is a low number an emergency? has the rest, and when should I go to the ER for low oxygen? answers the question people ask next.

Children’s numbers differ, so for a sick child, ask their doctor.