MSD Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Adherence to Drug Treatment


Shalini S. Lynch

, PharmD, University of California San Francisco School of Pharmacy

Reviewed/Revised Jul 2022 | Modified Sep 2022
Topic Resources

Adherence is the degree to which a person takes prescribed drugs as directed.

Adherence to (compliance with) drug treatment is important. However, only about half the people who leave a doctor's office with a prescription take the drug as directed. Among the many reasons people give for not adhering to drug treatment, forgetfulness is the most common. The key question then is: Why do people forget? Sometimes, the psychologic mechanism of denial is at work. Having a disorder causes concern, and having to take a drug is a constant reminder of the disorder. Or, something about the treatment, such as possible side effects, may greatly concern the person, resulting in a reluctance to follow the plan.

Reasons for Not Adhering to Drug Treatment

  • Forgetting to take the drug

  • Not understanding or misinterpreting the instructions

  • Experiencing side effects (the treatment may be perceived as worse than the disorder)

  • Finding the drug to taste or smell bad

  • Finding restrictions while taking the drug to be inconvenient (for example, having to avoid sunlight, alcohol, or milk products)

  • Having to take the drug very frequently or follow complicated instructions

  • Denying the disorder (repressing the diagnosis or its significance)

  • Believing that the drug cannot help or is not needed

  • Mistakenly believing that the disorder has been sufficiently treated (for example, thinking an infection is over just because the fever disappears)

  • Fearing dependence on the drug

  • Worrying about the expense

  • Not caring (being apathetic) about getting better

  • Encountering obstacles (for example, having difficulty swallowing tablets or capsules, having problems opening bottles, or being unable to obtain the drug)

  • Distrusting the health care practitioner

Results of not adhering

Most obviously, if a person does not adhere to treatment, symptoms may not be relieved or the disorder may not be cured. However, not adhering may have other serious or costly consequences. Not adhering is estimated to result in 125,000 deaths due to cardiovascular disease (such as heart attack and stroke) each year. In addition, it is thought that up to 23% of nursing home admissions, 10% of hospital admissions, and many doctor visits, diagnostic tests, and unnecessary treatments could be avoided if people took their drugs as directed.

Not only does not adhering add to the cost of medical care, it can also worsen the quality of life. For example, missed doses can lead to optic nerve damage and blindness in people with glaucoma, to an erratic heart rhythm and cardiac arrest in people with heart disease, and to stroke in people with high blood pressure. Not taking all prescribed doses of an antibiotic can cause an infection to flare up again and may be contributing to the problem of drug-resistant bacteria.

Children and adherence

Children are less likely than adults to take drugs as directed. In a study of children who had streptococcal infections and for whom a 10-day course of penicillin was prescribed, 56% were not taking the drug by the third day, 71% were not taking the drug by the sixth day, and 82% were not taking the drug by the ninth day. For children with chronic diseases such as type 1 diabetes or asthma, adherence is difficult to achieve because their treatment plan is complex and must be continued for a long time. Getting children to take drugs that do not taste good, seem frightening (such as eye drops or those that require a mask over the face), or require injections can also be difficult.

Sometimes parents do not understand a doctor's instructions. Also, parents (and patients themselves) forget, on average, about half the information 15 minutes after meeting with a doctor. They remember the first third of the discussion best and remember more about diagnosis than about the details of treatment. That is why doctors try to keep the treatment plan simple and often provide written instructions.

Older people and adherence

Although adherence is probably not affected by old age itself, it is affected by several factors that are common among older people, such as physical or mental impairments, the use of more drugs, and an increased risk of drug-drug interactions and side effects. Taking several drugs makes remembering when to take each drug harder and increases the risk of adverse drug-drug interactions Drug Interactions The effect a drug has on a person may be different than expected because that drug interacts with Another drug the person is taking (drug-drug interaction) Food, beverages, or supplements the... read more , particularly when over-the-counter drugs Precautions With Over-the-Counter Drugs Certain groups of people, such as the very young, the very old, the very sick, and pregnant and breastfeeding women, are more vulnerable to harm from drugs, including over-the-counter (OTC)... read more are also being taken. Doctors may be able to simplify the drug regimen—by using one drug that serves two purposes or by reducing the number of times a drug must be taken—to improve adherence and to reduce the risk of interactions.

Because older people are generally more sensitive to drugs than younger people, they are more likely to have adverse drug reactions and may require a lower dose of certain drugs (see Aging and Drugs Aging and Medications Medications, the most common medical intervention, are an important part of medical care for older people. Without medications, many older people would function less well or die at an earlier... read more Aging and Medications ).

Improving adherence

People are more likely to adhere to treatment if they have a good relationship with their doctor and pharmacist. Such relationships involve two-way communication.

Communication can start with an information exchange. By asking questions, doctors can help people come to terms with the severity of their disorder, intelligently weigh the advantages and disadvantages of a treatment plan, and ensure that they understand their situation correctly. By discussing their concerns, people can learn that denial of their disorder and misconceptions about their treatment can lead to forgetting to take drugs as directed, resulting in unwanted effects. Doctors and pharmacists can encourage adherence by providing clear explanations about how to take the drugs, why the drugs are necessary, and what to expect during treatment. When people know what to expect from a drug, good and bad, they and the health care practitioners involved in their care can better judge how well the drug is working and whether potentially serious problems are developing. Written instructions help people avoid mistakes caused by poor recall of their discussions with the doctor and pharmacist.

Good communication is important, particularly when people have more than one health care practitioner, because it ensures that all practitioners know all the drugs prescribed by the others, and an integrated treatment plan can be developed. Such a plan can help reduce the number of side effects and drug-drug interactions Drug Interactions The effect a drug has on a person may be different than expected because that drug interacts with Another drug the person is taking (drug-drug interaction) Food, beverages, or supplements the... read more and possibly result in a simpler drug regimen.

Participating in decisions about their treatment plan makes people more likely to adhere to it. By participating, people take responsibility for the plan and are therefore more likely to follow it. Taking responsibility includes helping monitor the good and bad effects of treatment and discussing concerns with at least one of their health care practitioners—doctor, physician’s assistant, pharmacist, or nurse. Even if the doctor, pharmacist, or other health care practitioner does not ask, people should report unwanted or unexpected effects rather than adjust a drug dose or discontinue a drug on their own. When a person has good reasons for not following a plan and explains them, the doctor or other health care practitioner can usually make an appropriate adjustment. It is wise for people to keep an up-to-date list of all of their drugs and to take it with them to any health care appointments.

Believing that their health care practitioner cares also makes people more likely to adhere to the treatment plan. People who receive explanations from a concerned practitioner are more likely to be satisfied with the care they receive and to like the practitioner more. The more people like the practitioner, the more likely they are to adhere.

Obtaining all drugs from one pharmacist can also help, because pharmacists keep computerized records of the drugs a person is taking and can monitor them for possible duplication and for drug-drug interactions. People taking prescription drugs should inform their pharmacist about what over-the-counter drugs and dietary supplements Overview of Dietary Supplements Dietary supplements are used by about 75% of Americans. They are the most common therapies included among integrative medicine and health (IMH) and complementary and alternative medicine (CAM)... read more (such as medicinal herbs) they are taking. Also, people can ask the pharmacist about what to expect from a drug, how to take it correctly, and which drugs interact with each other.

Support groups for people with particular disorders are often available. These groups can often reinforce the importance of following a treatment plan and provide suggestions for coping with problems. Names and telephone numbers of support groups can be obtained through local hospitals and community councils.

Memory aids can help people remember to take their drugs. For example, reminder cards can be placed in different areas of the home, or taking a drug can be associated with a specific daily task, such as brushing teeth. A wristwatch that beeps can be used as a reminder of when to take a drug. A health care practitioner or the person can mark the drug dose and the time of day to take it and the person can mark it on a calendar. When the drug is taken, the person checks the appropriate space.

Containers that help people take drugs as instructed can be provided by a pharmacist. Daily doses for a month may be packaged in a blister pack marked with calendar days, so that people can keep track of doses taken by noting the empty spaces. Caps or stickers the same color as the tablet or capsule can be placed on each container to help people match the drug to the instructions on the container. Multicompartment medication organizers that contain compartments for each day of the week and/or for different times of each day can be used (see Drug Errors Drug Errors Drug errors are mistakes made by doctors, health care practitioners, pharmacists, and patients when drugs are prescribed, given, taken, or stored. Drug errors can make people ill and allow diseases... read more Drug Errors ). The person or caregiver fills the compartments on a regular basis, such as at the beginning of each week. By looking at the organizer, the person can determine whether the pills have been taken.

Containers with a computerized cap are available. These caps beep or flash at dosing time and can record how many times a container is opened each day and how many hours have passed since the last time the container was opened. Another alternative is a paging service with a beeper (available from subscriber-based telecommunications companies).

quiz link

Test your knowledge

Take a Quiz!