Medication adherence and the role of BNF Cautionary and Advisory Labels (CALs)
Medicines need to be taken as prescribed in order to deliver their intended benefits without causing harm to patients. Health professionals should therefore always give clear and understandable information about a medicine before prescribing.¹ This should cover what the medicine is, how it is likely to benefit the patient, and how to take it.
When a medicine is dispensed, the dispensing label gives instructions on how to take the medicine and the packaging also contains a detailed patient information leaflet. The pharmacist or other health professional should also counsel the patient about any new medicine. But patients do not always take the medicine as prescribed, a problem known as non-adherence.
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Case study
A patient who is taking several prescribed medicines for hypertension and asthma, as well as various vitamins and supplements bought over the counter, is prescribed a new medicine for hyperlipidaemia. The pharmacist provides clear guidance, instructing the patient to take one tablet at night.
Initially, the patient is able to follow the treatment plan well. But as the patient takes their other medicines in the morning the patient continually forgets to take the nightly dose. Over time, these lapses accumulate, compromising medication adherence, such that the patient’s lipid levels do not improve.
Clearly medication adherence can be a complex and challenging problem for both health professionals and patients.
British National Formulary (BNF) and BNF for Children (BNFC) include a standardised set of Cautionary and Advisory Labels (CALs) for dispensed medicines. In this article we examine how these labels can help support medication adherence in practice.
What is medication adherence?
NICE defines medication adherence as the extent to which a patient’s action matches the recommendations agreed between prescriber and patient.¹ More recently, the Specialist Pharmacy Service (SPS) highlighted the importance of medicines adherence in achieving therapeutic goals and improving patient outcomes, noting that non-adherence leads to reduced clinical benefit and generates significant waste.² There are a wide variety of factors that drive low rates of medication adherence, and these have implications for how the problem is managed in practice.
The World Health Organization noted over 20 years ago that adherence among patients with chronic diseases in developed countries averages only 50%, with even lower rates in developing countries.³
Recent literature suggests that this challenge persists, as studies indicate that rates of adherence have not improved much, ranging from about 30-80%, with 50% still regarded as an average for long-term conditions.² ³⁻⁶
Reasons for non-adherence
There are many reasons why people fail to stick to their recommended medication regimen. These may be broken down into the following categories:⁶
- Patient-related factors
- Therapy-related factors
- Healthcare system factors
- Socioeconomic factors.
Non-adherence is further classified as:² ⁷
- Intentional – where the patient chooses not to follow the treatment recommendations based on their beliefs and preferences.
- Unintentional – where the patient wants to follow the treatment recommendations but faces practical barriers such as forgetfulness or language barriers.
There are many techniques and interventions that health professionals can use in an attempt to improve adherence. These include face-to-face interventions, electronic patient reminders (such as text messages or mobile apps), and strategies that enhance self-management (such as cognitive behaviour change).⁸
A meta-analyses and systematic review which aimed to identify effective interventions for improving medicines adherence concluded that, although there is a large evidence base for interventions, it is limited by risk of bias, making it difficult to draw definitive conclusions on which interventions are most effective.
One of the key actions identified to support adherence was the provision of reminders or prompts to patients about how to take their medicines. Cautionary and Advisory Labels (CALs) are one such prompt, providing targeted guidance at the point of dispensing.
How CALs support medication adherence
BNF CALs are a standardised set of guidance statements applied to dispensed medicines to ensure their safe and effective use.⁹ They provide crucial, concise supplementary advice regarding administration, storage, and how to avoid potential side effects and drug interactions. The following are examples of how CALs are used:
- many medicines can cause drowsiness and a label warns patients that if they feel sleepy they should not drive or use machinery
- to be effective some medicines need to be taken either before or after food and several CALs cover these instructions
- some medicines can colour the urine and a CAL warns about this so that patients are not unduly worried if this occurs.
While CALs should not replace effective and thorough clinical advice, they can reinforce advice, helping to solidify messages that may only be briefly covered during face-to-face discussions. This can support medicines adherence.
How CALs can enhance patient understanding
CALs have a role in enhancing a patient’s understanding of their medication. For example, they may prompt the patient to refer to the patient information leaflet for more detailed information about the guidance. While health professionals try to avoid using complex medical terminology during patient consultations, the language used can still be complex from a patient’s perspective.¹⁰ Importantly, CALs have all been user-tested, to ensure good understanding.
Several CALs relate to how to administer a medicine. For example, some antibiotics need to be taken for a specific number of days and it is important to complete the course. One of the CALs reinforces this by highlighting practical points such as spacing doses evenly throughout the day and continuing the medicine until the full course is completed, unless advised otherwise.
How CALs can support safe use of medicines
Patient misunderstanding about how to take their medicines is a common cause of medication errors which may result in serious and even fatal events.¹¹ In addition, harmful side effects caused by the misuse or incorrect use of a medicine can lead to a patient discontinuing treatment due to unwanted effects.¹² For example, unpleasant side effects such as dyspepsia or oesophageal irritation can often be avoided if the medicine is taken with food or with plenty of water and CALs giving this advice may prevent people stopping the medicine. Some CALs also give guidance on how to avoid harmful drug-drug interactions (e.g. antacids can interfere with the action of tetracycline antibiotics) as well as drug-alcohol interactions.
Patients taking over the counter (OTC) medicines may not be aware of whether they can be taken together with their prescribed medicines. This is especially important for medicines like paracetamol and aspirin that can be harmful in excessive doses. CALs alert patients to this by clearly flagging when these analgesics are components. They also highlight warnings that might otherwise be overlooked, such as the need to avoid sunlight with medicines that can cause serious photosensitivity reactions.
Some medicines can significantly impair driving ability and increase the risk of accidents. CALs recommended for these medicines give cautionary advice that alerts patients about effects that could impair their ability to drive or use equipment safely.
Shared decision making and CALs
Patient empowerment allows people to become more involved in their healthcare and treatment options.¹³ ¹⁴ Shared decision making, when a patient and their health professional make joint decisions about care, moves away from an authoritative approach and empowers people to choose treatments based both on evidence and their preferences, beliefs and values. Information targeted at patients, including CALs, may increase patient knowledge of medicines, enabling them to take a more active role in managing their health.
As of 12 May 2026 CALs are available in the following additional languages: Czech, French, Hindi, Nepali, Slovak, Somali, and Sri-Lankan Tamil.
The role of CALs where there are language barriers
For many patients, language barriers are a significant obstacle to medicines adherence. Patients who do not speak English as a first language or have limited health literacy may find verbal or written instructions difficult to interpret, negatively impacting how medicines are taken and increasing safety risks.¹⁵
To support patients whose first language is not English, CALs are available in the most commonly spoken languages in the UK, including Welsh, Arabic, Bengali, Polish, Punjabi, Spanish and Urdu. This practical step improves access to medicine information for populations who may be less likely to take their medicines as intended.¹⁵
The translations have been undertaken by professional registered translators and, where multiple dialects exist for a particular language, the CALs have been translated into the dialect most spoken. The availability of translated CALs also helps health professionals care for patients with limited English proficiency, by reinforcing critical instructions alongside verbal counselling. An example might be a Polish‑speaking patient who is newly prescribed a steroid cream that should be applied sparingly to the skin. If the CAL is provided only in English, this instruction may not be understood, but including it in Polish could reduce the likelihood of dosing errors and support more effective medicines use.
Conclusion
Non-adherence to medicines is a significant public health issue that presents considerable challenges for both patients and health professionals. It should not be seen as the patient’s problem,¹ as it is a complex and multifactorial issue, with many potential causes. Improving adherence requires multiple approaches, including better recognition of the problem by health professionals and approaches that are tailored to each patient’s individual circumstances. Understanding the reasons behind patient non-adherence can help health professionals work with patients to improve understanding and alleviate concerns.
CALs are a practical tool that can improve patient adherence alongside patient counselling and patient information leaflets. By reinforcing key information about how to take the medicine, CALs are an important tool in a wider set of interventions designed to support safe and effective medicines use.
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References:
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