Low battery symbol
The batteries are running down. On several models a flashing symbol still allows readings, while a steady symbol shown on its own means the thermometer will no longer measure.
Check your thermometer’s manual — makers differ.
What it is for
Replace the batteries with the type printed in your manual. Braun’s ThermoScan manual says to “Insert new batteries when the battery symbol appears on the display”; Microlife’s IR 310 manual says that if only the battery icon is shown “the battery should be replaced immediately”.
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 a temperature is a fever or what to do about it; only your own thermometer’s manual and your doctor or nurse can do that for the person you are looking after.
- What it looks like
- A battery outline, steady or flashing. Some Microlife thermometers use a triangle or an upside-down triangle instead.
- Names makers use
- Battery symbol (Braun, Omron, Beurer, Withings); Triangle or upside-down triangle (Microlife); Flashing battery icon (Braun No touch, Microlife IR 310 and NC 200)
Where makes differ
Braun’s ThermoScan manual separates two states: “Battery is low, but thermometer will still operate correctly” and “Battery is too low to take correct temperature measurement.” Braun’s No touch BNT 400 manual says the symbol flashes when 20% of battery life is left and the thermometer keeps working, while a steady icon shown alone means it “cannot work”. Omron’s ET720 table has one row for a low battery and another for an icon that “Remains on the display”, meaning the battery is depleted. Microlife’s MT 410 stick thermometer uses an upside-down triangle, and its IR 310 flashes the battery icon at switch-on as a reminder. The batteries differ as well: two AA cells in the Braun ThermoScan, two AAA cells in the Microlife IR 310 and NC 200, the Beurer FT 90 and FT 95 and the Withings Thermo.
What it does not mean
It is not Lo, which is about the temperature measured. The triangle on a Microlife MT 410 is not a hazard sign: Microlife’s manual says that when the upside-down triangle appears “the battery is flat and needs replacing”.
Sources
No published standard we could check defines the symbols on a digital thermometer’s display, so this meaning is taken from 5 makers’ own manuals and support pages, each fetched and read on the date shown:
- Braun: Braun ThermoScan 7 (IRT 6520) and ThermoScan 3 (IRT 6030) infrared ear thermometers — instruction manual (Asia-Pacific, PDF) — Replacing the batteries: two 1.5 V type AA (LR 06) batteries, “Insert new batteries when the battery symbol appears on the display”; error table: battery low but still operating correctly, and too low to measure. Checked 2026-09-29.
- Braun: Braun No touch + forehead thermometer BNT 400 — instruction manual (Asia-Pacific, PDF) — Errors and troubleshooting: “When 20% of battery life is left, the display flashes the low battery warning symbol”; “If the steady battery icon is the only symbol shown on the display, the device cannot work.” Checked 2026-09-29.
- Omron: Omron No-Touch Forehead Thermometer ET720 (MC-720-Z) — instruction manual (US, 5681249-5D, PDF) — The Icons and Error Messages: “Battery is low. Replace the battery.”; an icon that “Remains on the display”: “The battery is depleted. Change to a new battery.” Checked 2026-09-29.
- Microlife: Microlife Ear Thermometer IR 310 — instruction manual (IB IR 310 N-V10, revision 2024-09-13, PDF) — Low battery indicator: the icon “will keep flashing to remind the user to replace the battery”; flat battery: “If only the icon is shown on the display, the battery should be replaced immediately”; 2 × AAA. Checked 2026-09-29.
- Microlife: Microlife MT 410 digital stick thermometer — instruction manual (IB MT 410, revision 2025-07-03, PDF) — Battery installation and replacement: “When the «» symbol (upside-down triangle) appears in the display, the battery is flat and needs replacing.” Checked 2026-09-29.
- Beurer: Beurer FT 95 non-contact thermometer — instructions for use (2021-06-22, PDF) — Display description: battery status indicator; error messages: “The batteries are empty. Replace the batteries.”; two AAA (LR03) batteries. Checked 2026-09-29.
- Withings: Withings Thermo — regulatory information and troubleshooting (PDF) — Troubleshooting: “Low battery icon” — “Battery is low” — “Replace batteries”. Checked 2026-09-29.
Written in our own words; quotations are the makers’ wording.