Medication reconciliation is a structured, five-step process: build a complete list of what a patient currently takes, build a list of what’s being prescribed, compare the two, resolve any differences, and communicate the final list to the patient and their care team. It sounds straightforward, but medication errors harm an estimated 1.5 million people each year in the United States, and most of those errors happen during transitions of care, such as hospital admission, discharge, or transfer between units. Getting reconciliation right is one of the most effective ways to prevent those errors.
The Five Core Steps
The process follows a consistent framework regardless of the clinical setting.
Step 1: Build the current medication list. This is often the hardest and most time-consuming step. You’re creating what’s known as a Best Possible Medication History (BPMH), a thorough, verified record of every medication the patient actually takes. This goes well beyond glancing at a chart or asking “what meds are you on?” (More on how to do this well below.)
Step 2: Build the list of medications to be prescribed. This is the set of orders the provider intends to write for this encounter, whether that’s an admission order set, a new outpatient prescription, or a discharge medication list.
Step 3: Compare the two lists side by side. Go medication by medication. For each drug, check the name, dose, route, and frequency against both lists. Flag anything that doesn’t match.
Step 4: Make clinical decisions about each discrepancy. Every difference needs a deliberate choice: is this an intentional change (a dose increase, a discontinued drug) or an unintentional one (something was accidentally left off)? If intentional, document the reason. If unintentional, correct it.
Step 5: Communicate the updated list. The final, reconciled medication list goes to the patient (in language they understand), their caregivers, and any receiving providers. At discharge, this means a clear take-home medication list. At a clinic visit, it means an updated record in the chart and a conversation with the patient about what changed and why.
How to Build a Best Possible Medication History
The BPMH is the foundation of accurate reconciliation, and it requires more than a single question. A routine medication history pulls from whatever’s in the chart. A BPMH uses multiple sources, open-ended questions, and systematic prompts to capture what the patient actually takes, not just what’s been prescribed.
Start with the patient interview. Use open-ended questions and give the patient time to think. Useful prompts include asking about each medication’s purpose (“What do you take it for?”), packaging (“Are your medications in bottles, blister packs, or pouches?”), and barriers (“Is there anything that makes taking your medications difficult, like cost, trouble swallowing, or difficulty remembering?”). Ask specifically about adherence: “Do you ever forget to take your medication? What do you do when that happens?” Ask whether anyone at home helps them manage their medications.
Don’t stop at prescription drugs. Prompt specifically for over-the-counter medications, vitamins, supplements, herbal products, eye drops, inhalers, creams, and patches. People often don’t think of these as “medications” unless you ask directly. Lifestyle substances matter too: alcohol (type and frequency), tobacco, caffeine, and recreational drugs can all interact with prescribed medications and should be part of the history.
Then verify the patient’s account against at least one additional source. Reliable secondary sources include pharmacy dispensing records (call the pharmacy or check the electronic fill history), previous discharge summaries, the patient’s own pill bottles or medication list, and records from other prescribers. The patient’s self-report is the gold standard because only they know what they actually take, but cross-referencing catches gaps on both sides. Studies have found that discrepancies often stem from incorrect information pulled from health information systems or from simply not asking patients about certain medications.
Common Types of Discrepancies
When you compare the two lists, you’re looking for specific categories of mismatch. The most common type, by a wide margin, is omission: a medication the patient takes at home that doesn’t appear on the new order set. One systematic review found that omissions accounted for 63% of all discrepancies identified during reconciliation.
Other discrepancy types to watch for include:
- Dose or frequency differences: The patient takes 25 mg at home, but 50 mg was ordered on admission.
- Duplications: Two medications from the same class prescribed by different providers, or a brand name and its generic both appearing on the list.
- Drug interactions: A new medication that conflicts with something already on the home list.
- Unauthorized additions: A medication appears on the new list that the patient wasn’t taking and no one intended to start.
- Unclear information: Vague instructions like “take as needed” without specifying a maximum dose or indication.
The critical distinction for each discrepancy is whether it’s intentional or unintentional. An intentional discrepancy that’s properly documented (stopping a blood pressure medication because the patient’s readings are now normal) is fine. An intentional discrepancy that isn’t documented creates confusion for the next provider. An unintentional discrepancy is a potential error that needs to be corrected before it causes harm.
High-Risk Medications That Need Extra Attention
All medications deserve accurate reconciliation, but certain drug classes carry a higher risk of serious harm if something goes wrong. A useful memory aid is the acronym IHAPNCC, though most clinicians remember it as a checklist rather than a word.
Insulin tops the list because dosing errors are common and consequences are immediate. Blood thinners like warfarin and heparin require careful dose monitoring since even small errors can cause dangerous bleeding or leave a clot untreated. Opioid painkillers and sedatives carry risk of respiratory depression when doses are accidentally increased or when two similar drugs overlap. Chemotherapy drugs are especially dangerous with frequency mistakes: methotrexate, for example, is sometimes accidentally prescribed daily instead of weekly, which can cause severe toxicity. Potassium and other concentrated electrolytes given intravenously can cause cardiac arrest if prepared or dosed incorrectly.
When time is limited, prioritize reconciling these classes first. Errors involving these medications are more likely to cause serious, irreversible harm.
Reconciliation at Each Transition of Care
Medication reconciliation isn’t a one-time event. It should happen at every point where a patient’s medication orders change hands.
At hospital admission, the goal is to compare the BPMH against the admission orders. This is where most omission errors occur: a patient’s home medications simply don’t get ordered because no one captured them. At transfer between units (moving from intensive care to a general floor, for example), medications started temporarily may need to be stopped, and home medications that were held may need to be restarted. The reconciliation at this point ensures nothing falls through the gap between care teams.
Discharge is the highest-risk transition. The patient is going home, often with a changed medication regimen, and there may not be a pharmacist or nurse watching for errors once they leave. The discharge reconciliation should clearly distinguish which medications are new, which have changed doses, and which have been stopped. One study at an academic medical center found that pharmacy-led discharge counseling combined with reconciliation reduced hospital readmissions by 27%. Among the patients who actually received the full pharmacy intervention, readmissions dropped even further, from 26% to about 16%. For high-risk heart failure and pneumonia patients, the reduction reached 34%.
Outpatient visits require reconciliation too. Every clinic appointment is a chance to review the list, catch medications that were started or stopped by other providers, and update the record. This is especially important for patients seeing multiple specialists who may not be coordinating directly.
Making the Process Work in Practice
The MATCH toolkit, developed by the Agency for Healthcare Research and Quality, outlines an eight-step implementation approach for organizations trying to improve their reconciliation process. The steps include assembling an interdisciplinary team, mapping the current reconciliation workflow, identifying weak points, establishing how you’ll measure improvement, designing changes, piloting them, training staff, and evaluating results. This structured approach helps because reconciliation failures are usually system problems, not individual mistakes.
At the individual level, a few practical habits make the process more reliable. Keep a checklist of medication categories to prompt patients: heart medications, breathing medications, diabetes medications, pain medications, mental health medications, hormones, eye drops, skin creams, supplements. People tend to recall medications in clusters by condition rather than by name. If the patient brought pill bottles, use them. If they have a written list, start there but don’t trust it completely since lists go out of date. Always ask the patient directly rather than relying solely on the electronic record, because the chart reflects what was prescribed, not necessarily what the patient actually takes.
Document your work clearly. For each discrepancy you identify, note whether the difference was intentional or unintentional, what action was taken, and who was informed. This documentation protects the patient at the next transition, when a different provider will rely on your reconciled list as their starting point.