Encounter for therapeutic drug level monitoring

• Z codes represent reasons for encounters. A corresponding procedure code must accompany a Z code if a procedure is performed. Categories Z00-Z99 are provided for occasions when circumstances other than a disease, injury or external cause classifiable to categories A00-Y89 are recorded as 'diagnoses' or 'problems'. This can arise in two main ways:
• (a) When a person who may or may not be sick encounters the health services for some specific purpose, such as to receive limited care or service for a current condition, to donate an organ or tissue, to receive prophylactic vaccination (immunization), or to discuss a problem which is in itself not a disease or injury.
• (b) When some circumstance or problem is present which influences the person's health status but is not in itself a current illness or injury.

Categories Z40-Z53 are intended for use to indicate a reason for care. They may be used for patients who have already been treated for a disease or injury, but who are receiving aftercare or prophylactic care, or care to consolidate the treatment, or to deal with a residual state

follow-up examination for medical surveillance after treatment (Z08-Z09)

follow-up examination after treatment (Z08-Z09)

condition requiring care

holiday relief care (Z75.5)