Low battery on a pulse oximeter
The batteries are running low. The oximeter still works for now, but it may switch off or fail to start soon, and a weak battery is one of the reasons the manuals give for a display that goes blank.
Check your oximeter’s manual — makers differ.
What it is for
Replace the batteries, usually two AAA cells, both at once. Masimo’s troubleshooting table says, for a red battery symbol, “Replace low batteries as soon as possible.” Microlife says of the OXY 300: “Replace the batteries when the low power indicator appears on the display. Always replace both batteries at the same time.” Nonin says the same for the 9590: “Replace low batteries as soon as possible.”
These pages report what each maker’s manual says and quote it wherever health is involved. They do not diagnose anything, they are not medical advice, and they do not tell you whether an oxygen or pulse reading is right for you or what to do about it; only your own oximeter’s manual and your doctor or nurse can do that for the person you are looking after.
- What it looks like
- A battery outline, empty or turned red, in a corner of the screen; on a Nonin 9590, numbers that flash.
- Names makers use
- Numeric displays flash once per second (Nonin Onyx Vantage 9590); Red battery symbol (Masimo MightySat Rx); Battery level indicator (Beurer PO 30 and PO 60); Low battery indicator (Microlife OXY 300, Beurer PO 45)
Where makes differ
Nonin’s 9590 has no battery icon: Nonin says that “when batteries are low, the numeric displays flash once per second”. Masimo turns its battery symbol red. Beurer’s PO 30 and PO 60 manuals list a battery level indicator among the display items.
What it does not mean
It is not a signal or reading problem, and the numbers shown are not flagged as wrong by it. On a Nonin 9590 the flashing numbers are about the batteries, not about the reading.
Sources
No published standard we could check defines what a fingertip pulse oximeter’s display shows, so this meaning is taken from 4 makers’ own manuals and support pages, each fetched and read on the date shown:
- Nonin: Nonin Onyx Vantage 9590 finger pulse oximeter — instructions for use (P/N 10906-001-04, 2020, PDF) — Installing batteries: “When batteries are low, the numeric displays flash once per second.” “Replace low batteries as soon as possible.” Checked 2026-09-29.
- Masimo: Masimo MightySat Rx fingertip pulse oximeter — home care manual (PDF) — Troubleshooting: “A red battery symbol displays on Main Screen” — low battery — “Replace low batteries as soon as possible.” Checked 2026-09-29.
- Microlife: Microlife OXY 300 fingertip pulse oximeter — instruction manual (IB OXY 300 N-V9, revision 2023-11-30, PDF) — Explanation of symbols: 6 Low battery indicator; “Replace the batteries when the low power indicator 6 appears on the display. Always replace both batteries at the same time.” Checked 2026-09-29.
- Beurer: Beurer PO 30 pulse oximeter — instructions for use (2020-01-08, German/English, PDF) — Display description: 5. Battery level indicator. Checked 2026-09-29.
- Beurer: Beurer PO 45 pulse oximeter — instructions for use (2020-06-12, German/English, PDF linked from beurer.com) — Signs and symbols: Low power indication; features: low battery indicator. Checked 2026-09-29.
Written in our own words; quotations are the makers’ wording.