TDM (Therapeutic Drug Monitoring)

TDM measuring the blood levels of a drug. TDM can be used for most drugs except NRTIs (nukes).

TDM is only used in certain situations.

  • To check for a drug interaction. This can be important with new drugs.
  • With pre-existing liver or kidney damage. Or in people with haemophilia, and some other medical conditions. If your liver is damaged it might process drugs more slowly. TDM can find the safest dose.
  • If you are not absorbing drugs. For example, if you have severe diarrhoea.
  • For children. Differences in growth rates and the way children process drugs at different ages is complicated. Even when doses are calculated by body weight or body surface area they often need altering.

TDM is recommended in UK guidelines in these and other situations. Poor drug absorption or faster clearance can cause a combination to fail.

Using TDM and resistance tests together produces better results than either test alone.

TDM in the UK is available from Lab21:

Last updated: 1 August 2021.