Measuring radiation exposure

The low levels of radiation you are exposed to during medical tests can be measured in units called millisieverts (mSv).

Some examples of different levels of radiation exposure are listed below.

  • asingle chestX-ray (0.014 mSv) equivalent to three days of natural background radiation (read more about the risks of X-rays )
  • a mammogram (0.4 mSv) the amount of radiation a woman receivesduring a mammogram of both breasts (a type of X-ray used during breast cancer screening); the benefit of detecting breast cancer at an early stage is likely to outweigh the risk of any problems from the radiation exposure
  • natural radiation (2.7 mSv) the average annual dose a person in the UK receives from natural sources
  • acomputerised tomography (CT) scan of the wholespine (10 mSv) thedose is lower for a CT scan of the head or chest; the benefits of havinga CT scan usually greatly outweigh any potential risk(read more about the risks of CT scans )
  • working with radiation (20 mSv) the UK legal limit that a classified person who works with radiation may be exposed to in any given year (as set by the Ionising Radiations Regulations 1999); however, most workers receive considerably less than this

Want to know more?

  • GOV.UK: patient dose information
  • Health and Safety Executive: ionising radiation FAQs
  • World Health Organization: what is ionising radiation?
Content supplied by the NHS Website

Medically Reviewed by a doctor on 21 Dec 2018