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How to choose a thermometer: mercury, digital or infrared

Mercury, gallium, digital and infrared thermometers: how they differ and how to take a temperature correctly.

  • First aid
  • Baby Care
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A thermometer is the first thing every home medicine cabinet needs. Here is how the four types differ and how to take a temperature so the reading is accurate.

Types of thermometer

Mercury thermometer

The classic glass thermometer. Accurate and inexpensive, but a reading takes 7–10 minutes and the glass breaks easily. Shake it down below 35 °C before each use.

Medical mercury thermometer

Mercury-free (gallium) thermometer

Looks like a mercury thermometer and is just as accurate, but contains a safe gallium-based liquid alloy. A good choice for families with children. Use it the same way: 7–10 minutes, shaken down first.

Mercury-free gallium thermometer

Digital thermometer

Shows a result in 30–60 seconds and beeps when done. Convenient for children. After the beep, keep it under the arm for another 1–2 minutes for a more accurate reading. Runs on a battery.

Infrared (no-contact) thermometer

Measures on the forehead in 1–2 seconds without waking a sleeping child. Handy for a quick check, but accuracy depends on distance and room temperature. If the reading is high, check again with a regular thermometer.

How to take a temperature under the arm

  • Dry the armpit.
  • Place the tip of the thermometer deep in the armpit.
  • Hold the arm against the body and stay still.
  • Don't measure right after eating, a hot shower or exercise — wait 20–30 minutes.

What temperature is normal

Under the arm, about 36.0–37.0 °C is normal. 37.1–37.9 °C is raised, and 38 °C or higher is a fever.

When to see a doctor straight away

  • A baby under 3 months has a temperature of 38 °C or higher.
  • The temperature is above 39 °C or lasts more than 3 days.
  • There is difficulty breathing, seizures, a rash, severe drowsiness or signs of dehydration.

If a mercury thermometer breaks

  • Take children and pets out of the room, open the window and close the door.
  • Don't use a vacuum cleaner or broom — they spread the mercury.
  • Collect the mercury beads with stiff paper or tape and put them in a jar with a tight lid.
  • Don't throw mercury in the bin or down the drain — call 911 and ask where to hand it in.

Not sure which to choose? Ask the pharmacist at any ABAPharm pharmacy or write to us in the site chat. All thermometers are in the catalog.

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