'''Compliance''' (or '''Adherence''') is a medical term that is used to indicate a patient's correct following of medical advice. Most commonly it is a patient taking medication ('''drug compliance'''), but may also apply to use of surgical appliances such as compression stockings, chronic wound care, self-directed physiotherapy exercises, or attending counselling or other courses of therapy.

Patients may not accurately report back to healthcare workers because fear of possible embarrassment, being chastised, or seeming to be ungrateful for a doctor's care.

Causes for poor compliance include:<ref name="BNF">''British National Formulary''. ''45'' March 2003.</ref>
*Forgetfulness
*Prescription not collected or not dispensed
*Purpose of treatment not clear
*Perceived lack of effect
*Real or perceived side-effects
*Instructions for administration not clear
*Physical difficulty in complying (e.g. opening medicine containers, handling small tablets, swallowing difficulties, travel to place of treatment)
*Unattractive formulation, such as unpleasant taste 
*Complicated regimen   
*Cost of drugs

==Adherence==
An estimated half of those for whom medicines are prescribed do not take them in the recommended way. Until recently this was termed "non-compliance", and was sometimes regarded as a manifestation of irrational behavior or willful failure to observe instructions, although forgetfulness is probably a more common reason. But today health care professionals prefer to talk about "'''adherence'''" to a regimen rather than "'''compliance'''".

There have been many studies of the effects of different strategies in improving adherence to therapy. These include reducing the frequency of administration during the day and reducing the numbers of medicines a patient has to take. However, there is no evidence that such measures are effective. 

Nevertheless, it seems likely that adherence can be improved by taking care to explain the benefits and adverse effects of a drug. In a busy clinic it is too easy for the prescriber to give out a prescription with little or no explanation. It also makes sense to reduce the frequency of taking medicine to once or twice a day: though again, there is no evidence that this tactic is effective.

==Drug compliance==
It is estimated that only 50% of patients suffering from chronic diseases in developed countries follow treatment recommendations.<ref name="WHOreport"> Sabaté, E. (ed.): "Adherence to Long term Therapies: Evidence for Action". ''Bandolier [http://www.jr2.ox.ac.uk/bandolier/booth/cardiac/patcomp.html Review] 2004</ref>
Again, the word “adherence” is preferred by many health care providers, because “compliance” suggests that the patient is passively following the doctor’s orders.  Patients should not be passive: a treatment plan must be based on a therapeutic alliance or contract between the patient and the physician. Yet at least one reference implies that both terms are flawed, giving no meaningful information. <ref>L. Osterberg and T. Blaschke, <u>Adherence to Medication<u>, N Engl J Med, '''2005'''(''353''):487-97.</ref>

===Prescription collection and dispensing===
In the past both doctor and patient expected that the end of a consultation should be marked by a prescription. However, many patients don't necessarily wish to commence a course of treatment, but merely seek reassurance as to the nature of their symptoms. It has been estimated that up to a third of prescriptions written by UK GPs do not go to the pharmacist.  A third of all dispensed medication is not taken in accordance with the prescribing instructions.

Patients may simply forget to bring the prescription to a pharmacist.  They may believe that the medication was not needed: the consultation provided reassurance, or pointed the way to self-care measures other than medication.  Some patients may alternatively believe that their condition does not yet warrant starting treatment, but that the prescription is only in place should the problem fail to resolve spontaineously or deteriorate.  Some of these patients are later unable to return to their doctor when their condition changes.

In der Medizin spricht man von der '''Compliance''' bzw. '''Komplianz''' des Patienten. Damit wird der Umstand angesprochen, dass die Heilung vieler Krankheiten ein kooperatives Verhalten des Patienten voraussetzt. Im medizinischen Sinn kann man Compliance also mit '''Therapietreue''' oder ''konsequentem Befolgen'' übersetzen, sprich, ob der Patient das tut, was der Arzt ihm vorschreibt. Besonders wichtig ist Compliance bei chronisch oder psychisch Kranken in Bezug auf die Einnahme von Medikamenten, dem Befolgen einer Diät oder der Veränderung des Lebensstils.

Compliance kann vorliegen, wenn der Patient

* von einer allgemeinen Krankheitsanfälligkeit überzeugt ist,
* sich seiner Erkrankung gegenüber für besonders anfällig hält,
* die Ernsthaftigkeit seines Leidens erkennt,
* an die Wirksamkeit der Therapie glaubt,
* mit der medizinischen Betreuung zufrieden ist oder
* von seinen Angehörigen in seinem Befolgungsverhalten unterstützt wird
* es nicht wagt, die Ratschläge des Behandlers nicht zu befolgen.

Therapietreue kann durch  Psychoedukation geschult werden.

Auf den Patienten bezogen bedeutet Compliance: die Bereitschaft, ärztlichen Anweisungen zu folgen. Auf den Adherence eingeführt worden.

Compliance in der Blistern gibt es auch elektronische Systeme, um die Tablettenentnahme zu überwachen und den Patienten akustisch oder optisch an die Einnahme des Arzneimittels zu erinnern. 

Das Nichteinhalten von ärztlichen Ratschlägen bzw. die Nichterfüllung von therapeutisch notwendigen Pflichten wird in diesem Zusammenhang als '''Non-Compliance''' bezeichnet. Von '''intelligenter Non-Compliance''' spricht man, wenn der Patient aufgrund eigener rationaler Überlegungen oder Beobachtungen (z. B. eines fehlenden Therapieerfolges oder einer starken Nebenwirkung) eine tatsächlich falsche oder nicht sinnvolle Therapieanweisung der Arztes bewusst missachtet. 