Adherence is the extent to which a person's behaviour matches the recommendations agreed with the prescriber. There are a number of factors that contribute to adherence. The causes of non-adherence are classified as intentional or unintentional. However, in reality, both types may occur to a certain extent in the same person.

Intentional non-adherence

This is where a patient decides not to follow the prescribed medicines regimen because of their personal beliefs or preferences. Each person will usually weigh up the risks and benefits of taking the medicines from their own perspective and then make a decision as to whether or not they start or continue taking them. If their concerns about the medicines are greater than their perceived need to take them, they are unlikely to adhere to the planned course of treatment.

Unintentional non-adherence

This is where a person wants to follow their medicines regimen but cannot because of barriers that are beyond their control. These barriers could include forgetfulness, a lack of understanding, or practical barriers, such as the inability to read labels, open containers or use devices.

Supporting adherence

Guidance from the National Institute for Health and Care Excellence (NICE) recognises that healthcare professionals should respect a person's decision not to take their medicines and be more open about the reality of nonadherence. It continues to point out that non-adherence is very common and that healthcare professionals should take a nonjudgemental approach, actively encouraging people to discuss non-adherence and any doubts or concerns they may have about their treatment.

There are some actions that have been found to be useful in supporting people to take their medicines. These include:

• Patients having a prompt card of the medicines they are taking to support their understanding and memory
• Encouraging the patient to self-monitor
• Simplifying the dose regimens
• Providing large print labels and patient information leaflets
• Changing the medicine, formulation, dose or timing to reduce side effects
• Offering repeat collection and delivery services
• Carrying out medicines use reviews (MURs).