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Can clients consent for health care if they have been using drugs or alcohol?


According to the law in British Columbia, every person 19 years of age and older has the right to give or refuse consent to health care when it is being offered, provided they have the capacity to consent.**
In obtaining informed consent for health care, clinicians should communicate how the clients will benefit from the health care intervention and warn them of reasonably foreseeable harms. In providing informed consent for health care, clients should demonstrate autonomy, understanding, rational thinking, and appreciation of their illnesses and express a choice to agree or refuse care.

Determining capacity to consent prior to obtaining informed consent can be particularly challenging with individuals who are thought to be vulnerable to coercion and manipulation due to homelessness or illicit substance (alcohol or drugs) use. It can also be difficult to assess this population if they recently used drugs or alcohol (or who are withdrawing from drugs or alcohol), as their cognition may be impaired.

**A clinician can provide health care without consent for a client to treat a new, unexpected condition that they discover while they are in the middle of giving the client other care that they already consented to if the client is unconscious or semi-conscious and if the condition is medically urgent. They may also provide health care if the client is unconscious, semi-conscious, impaired by drugs or alcohol if the care is required to save the client’s life, to prevent serious mental or physical harm, or to relieve extreme pain.

Summary of evidence

A recent study involving qualitative interviews with nurses who deliver care to individuals who misuse substances revealed that nurses often feel unsure about whether they should deliver care to some clients who may or not have impaired judgement due to substance use.  They expressed a need for a decision-making tool to guide their clinical practice.

A novel tool, called the Capacity Assessment Instrument for People who misuse Substances (CAIPS) has been developed to assist nurses with determining if their clients lack capacity to consent.  This 11-item questionnaire consists of statements that nurses can rate on a scale of 1-4, with higher scores indicating higher levels of consent.  These statements relate to understanding, voluntariness, orientation to person, place and time, ability to communicate, sustained attention, distorted reality, appreciation, reasoning, expression of choice, decision making demands, and physical indication of substance use.

The minimum score that can result from the CAIPS is 11 and the maximum score is 44.  Clients who have a score of less than 33 may be considered as lacking capacity to consent for care and the nurse may choose to delay care, if the care is not urgently needed, until the client is less impaired.

Information about the reliability and validity of the CAIPS instrument can be found here.  A PDF of the instrument is available for download at the bottom of this article, under Related Resources and can also be downloaded here.

Implications for practice

It is important to note that the CAIPS instrument is a guideline only and should be used in conjunction with other nursing assessments. In addition, the CAIPS instrument is a tool available when nurses feel unsure about whether their client lacks capacity to consent. It does not need to be applied in all nursing encounters that involve substance use.

For more information

For more information, contact Darlene Taylor at the BC Centre for Disease Control.


  1. BC Legislature. Health Care (Consent) and Care Facility (Admission) Act. 2013. Accessed online on 4 Aug 2014 at http://www.bclaws.ca/EPLibraries/bclaws_new/document/ID/freeside/00_96181_01
  2. Taylor D.  A Tool to Assess Capacity to Consent for Treatment Among Homeless Populations with Problematic Substance Use [dissertation], University of British Columbia, Vancouver BC, 2014.
  3. Nidus Personal Planning Resource Centre.  Health care consent: Your rights and the law.  Nidus personal planning resource centre and registry.  Vancouver, BC.  March 2012.  Available on line at http://www.nidus.ca/PDFs/Nidus_Info_HCC_Your_Rights_and_the_Law.pdf