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Medication Error Causes

Medication errors are mistakes made by physicians, nurses, and caregivers when they are administering a patient’s medication. These can include incorrect dosage, incorrect method of administration, and even providing the incorrect medication. Medication errors can also be made by patients and their family members if they are administering the medication themselves.

Medication errors are a serious and pervasive problem. Studies suggest that one in five nursing home residents suffer from medical errors, and 37% of those medical errors are medication errors. Though most medication errors have only minor health consequences, a small portion cause adverse drug effects that can be very harmful to the patient. Some possible consequences of medication error include:

  • Unexpected medical complications
  • Reduced immune response
  • Organ failure
  • Malnutrition and dehydration
  • Death

What Causes Medication Errors?

There are dozens of different possible causes of medication errors. Some of the most common causes include:

  • Misdiagnosis and incorrect prescription
  • Incorrect transcription of prescription or dose
  • Confusion regarding how to administer medication
  • Understaffed facilities and neglect
  • Unforeseen interactions with other prescriptions

The best way to understand the different causes of medication errors is to examine the four types of medication errors:

  • Knowledge based
  • Rule based
  • Action based
  • Memory based

Knowledge Based Errors

Knowledge based errors occur when there is a lack of knowledge that would affect the medication. For example, if the staff and patient did not know that the patient was allergic to penicillin, it could likely cause a knowledge based error. There is so much knowledge that doctor and medical staff need to properly treat a patient, and sometimes there is a gap between what they know and what they need to know.

The causes of knowledge based medication errors are lack of knowledge regarding a patient’s medical history, allergies, diet, other prescriptions, and other relevant medical information. Not knowing how two prescriptions will interact is also knowledge based cause of medication error.

Rule Based Errors

Rule-based errors occur when medical staff uses a bad rule or incorrectly applies a good rule. For example, if a certain drug should be injected through the thigh, but the nurse uses a different route, this would be a rule based error.

There are a few causes of rule based errors including:

  • Improperly trained medical staff
  • Inattention or exhaustion of medical staff
  • Confusion regarding rule
  • Unclear or incorrect prescription directions

Action Based Errors

These types of errors occur when medical staff has the right information and is trying to do things correctly, but inadvertently make a mistake. These are also called “slips.” These are the most common types of medication errors. Some examples of these errors include:

  • Writing down the wrong prescription
  • Picking up the wrong bottle from the pharmacy shelf
  • Misreading a prescription

The causes of these types of errors are inattention and exhaustion of staff, no crosschecking or failsafe systems in the nursing home, neglect, and inattention to detail. Not every mistake can be avoided, and these types of errors happen in even the best facilities, but a well-staffed and well-managed nursing home will have systems in place to catch these errors before they do serious damage.

Memory Based Errors

These types of errors are simple mental mistakes that affect how a medication is administered. One example of a memory based error is if a nurse forgets that a patient is allergic to a certain drug, and then accidentally administers it to them. Another example of a memory based error is if a nurse forgets to record that she administered the medication, and then a second nurse unnecessarily administers it again.

Memory based errors are difficult to prevent. Like action based errors, some mental mistakes are unavoidable, but a high quality nursing home staff will not suffer from excessive exhaustion or lack of time to properly treat each resident. With a staff that works together and helps each other, these types of medication errors can be reduced and caught before it is too late.


“About Medication Errors.” National Coordinating Counsel for Medication Error Reporting and Prevention. National Coordinating Counsel for Medication Error Reporting and Prevention, n.d. Web. 28 Feb 2014. <http://www.nccmerp.org/>.

Cheragi, Mohammad, Human Manoocheri, et al. “Types and Causes of Medication Errors from a Nurse.”Iranian Journal of Nursing and Widwifery Research. 18(3).May-June (2013): 228-231. Web. 28 Feb. 2014. <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3748543/>.

“Medication Errors.” U.S. Food and Drug Administration. U.S. Department of Health and Human Services, 08 Aug 2013. Web. 28 Feb 2014. <http://www.fda.gov/drugs/drugsafety/medicationerrors/default.htm>.


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