Fever colours and fever symbol (green, yellow or red screen)
The thermometer compared the reading with a fever threshold its maker built in, and shows which side of it the reading fell on. The threshold is the maker’s choice: it differs by brand and, on some thermometers, by the age you select.
Check your thermometer’s manual — makers differ.
What it is for
Read the number, not only the colour, and follow what your own manual says about fever. Braun’s ThermoScan manual: “Please consult your doctor if the thermometer shows elevated temperature (yellow or red background lights for IRT 6520).” Omron’s ET720 manual: “A high or prolonged fever requires medical attention, especially for small children. Please contact your doctor.” Withings’ user guide: “Make sure you consult a doctor should the fever and/or symptoms be persistent or worrying in any way.” Beurer’s FT 95 instructions: “If you are uncertain about interpreting the results or if the values are abnormal (e.g. fever), please consult your doctor.”
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
- The screen or a light glows green, yellow or red after a reading, or a small fever symbol appears next to the number; some beep several times as well.
- Names makers use
- AgeSmart colour-coded display (Braun); Fever alarm, red backlight (Microlife IR 310); High body temperature reminder (Microlife NC 200); Fever indicator, fever and no-fever symbols (Beurer); Fever status LED (Withings)
Where makes differ
The thresholds do not agree. Microlife’s IR 310 and NC 200 turn the screen red and beep ten times at 37.5 °C or higher, and show green below it. Beurer’s FT 95 lights green below 37.5 °C, yellow from 37.5 °C to 37.9 °C and red over 38 °C, and Beurer’s FT 90 shows its fever symbol from 38.0 °C (100.4 °F). Braun’s AgeSmart thermometers move the threshold with the age you select: Braun’s table turns red above 37.4 °C for babies up to 3 months, yellow above 37.6 °C and red above 38.5 °C from 3 to 36 months, and yellow above 37.7 °C and red above 39.4 °C from 36 months to adult. Braun’s No touch BNT 400 uses the same age table and beeps ten times for a reading in the fever range. Withings’ Thermo also sets its LED colour by the age range of the person, and the Withings app labels readings normal, mild fever or high fever. Omron’s ET720 manual describes no fever colour at all: its display lights up for 5 seconds after every reading.
What it does not mean
A green screen is not an all-clear: Braun’s No touch manual says that if it shows 36.4 °C (97.5 °F) or less with a green or white backlight and the person has unusual symptoms, you should contact your physician or health care professional. The colour does not know where you measured, and Microlife’s manuals give different normal ranges for the armpit, mouth and rectum, so readings from different sites are not the same scale.
Other symbols with the same shapes
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) — AgeSmart color-coded display: “A green screen suggests no fever, a yellow screen suggests moderate fever, and red signals high fever”; the temperature table by age (0–3 months, >3–36 months, >36 months to adult); “Please consult your doctor if the thermometer shows elevated temperature”. Checked 2026-09-29.
- Braun: Braun No touch + forehead thermometer BNT 400 — instruction manual (Asia-Pacific, PDF) — The same AgeSmart age table; “If the temperature is in the fever range, 10 short beeps will sound”; the note on readings of 36.4 °C (97.5 °F) or less with a green or white backlight. Checked 2026-09-29.
- Microlife: Microlife Ear Thermometer IR 310 — instruction manual (IB IR 310 N-V10, revision 2024-09-13, PDF) — Fever alarm: “10 short beeps and a red LCD backlight alert the patient that he/she may have a temperature equal to or higher than 37.5 °C”; backlight green for 5 seconds below 37.5°C / 99.5°F. Checked 2026-09-29.
- Microlife: Microlife NC 200 non-contact thermometer — instruction manual (IB NC 200-e N-V10, 2026-08-17, PDF) — High body temperature reminder: “10 short beeps and a red LCD backlight reminds the patient that they may have a temperature equal to or higher than 37.5 °C.” Checked 2026-09-29.
- Beurer: Beurer FT 95 non-contact thermometer — instructions for use (2021-06-22, PDF) — Forehead measurement: fever indicator green below 37.5 °C (99.5 °F), yellow between 37.5 °C and 37.9 °C, red over 38 °C (100.4 °F) with the fever symbol; Beurer tip on consulting your doctor. Checked 2026-09-29.
- Beurer: Beurer FT 90 non-contact clinical thermometer — instructions for use (2021-06-22, PDF) — Display description: “Measurement ≥ 38.0°C (≥100.4°F) “fever””, “< 38.0°C (<100.4°F) “no fever””; three beeps at 38 °C or higher if the signal is on. Checked 2026-09-29.
- Withings: Withings Thermo — user guide (v2.0, April 2018, PDF) — Understanding the fever status LED: “The color of the LED indicates at a glance whether or not the person has a fever. This is based on the temperature and the user’s age range”; normal, mild fever and high fever in the app; the safety note on consulting a doctor. Checked 2026-09-29.
- Omron: Omron No-Touch Forehead Thermometer ET720 (MC-720-Z) — instruction manual (US, 5681249-5D, PDF) — Taking a Reading: “The display lights up for 5 seconds”; Important Safety Information: “A high or prolonged fever requires medical attention, especially for small children. Please contact your doctor.” Checked 2026-09-29.
Written in our own words; quotations are the makers’ wording.