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Thermometers

A clinical thermometer is a medical device under EU law. The main types sold in parapharmacies are digital contact thermometers, liquid-in-glass galinstan thermometers, and infrared tympanic and forehead thermometers. Mercury thermometers have been removed from the EU consumer market.

Regulatory class

Clinical thermometers fall within the definition of medical device in Article 2(1) of Regulation (EU) 2017/745: they are instruments intended for use in the diagnosis or monitoring of a human physiological state. They bear the CE mark and are classified under the MDR's Annex VIII rules. Non-active liquid-in-glass thermometers are typically Class I with a measuring function, for which notified-body involvement is limited to the metrological aspects; electronic (active) thermometers are commonly classified in Class IIa, depending on intended purpose. The manufacturer's classification is reflected in the notified-body number accompanying the CE mark.

The end of mercury

Mercury fever thermometers have been progressively removed from the EU consumer market. Under entry 18a of Annex XVII of Regulation (EC) No 1907/2006 (REACH), mercury may not be placed on the market in fever thermometers (since April 2009) or in other measuring devices intended for sale to the general public. Regulation (EU) 2017/852 on mercury additionally prohibits the manufacture, import and export of most mercury-added non-electronic measuring devices, including thermometers. The restriction reflects the toxicity of mercury and the environmental risks associated with breakage and disposal. The result is that a contemporary parapharmacy will not sell mercury fever thermometers; if a household still has one, the appropriate disposal route is the hazardous-waste collection of the local authority.

Galinstan (liquid-in-glass, mercury-free)

Galinstan thermometers use a eutectic alloy of gallium, indium and tin in place of mercury. They look like traditional liquid-in-glass thermometers, do not contain mercury, and are subject to the MDR like any clinical thermometer. The measurement principle is the thermal expansion of the metal alloy in a calibrated capillary.

Digital contact thermometers

Digital contact thermometers use a thermistor or similar electronic sensor in the tip of a probe. They are usually placed in the mouth, axilla or rectum, with the manufacturer's instructions specifying which body sites the device is calibrated for and the corresponding adjustments to the displayed temperature. They produce a numerical reading and typically have a hold function for the last measured value.

Infrared tympanic and forehead thermometers

Infrared thermometers measure the thermal radiation emitted by the body surface (forehead) or by the tympanic membrane and surrounding tissues (ear) and convert this to a calculated body temperature. They are convenient, non-contact in the case of forehead devices, and fast. Their accuracy depends on correct technique — distance to skin, target area, environmental conditions — and on the device's specific calibration. As with any clinical thermometer, the instructions for use specify the conditions of valid measurement.

Accuracy and the relevant standards

Several harmonised standards address the requirements for clinical thermometers:

• EN ISO 80601-2-56 — particular requirements for the basic safety and essential performance of clinical thermometers for body temperature measurement.
• EN ISO 80601-2-61 — particular requirements for pulse oximeter equipment (a separate category, but in the same family of devices).
• EN 12470 series — earlier standards for clinical thermometers (including mercury-in-glass, compact electrical and infrared ear thermometers); the parts covering electrical and infrared ear thermometers have been superseded by EN ISO 80601-2-56.

The accuracy specification, in terms of maximum permissible error and the range over which it applies, is part of the manufacturer's declaration of conformity and is verifiable from the device documentation.

For consumers

This site does not interpret temperature readings or give advice on when to seek medical care. For interpretation of body temperature in any specific situation — and particularly for fever in infants, young children, the elderly and people with chronic conditions — the appropriate advice is from a pharmacist or a physician. The label-literacy points above are about understanding what a thermometer is and what its specifications mean.

Last reviewed: October 2026.