MAR chart codes explained: what every code on a MAR sheet means

MAR chart codes are the short letters a care worker writes on a medication administration record when a dose is not given in the normal way. The common ones are R for refused, O for omitted, H for in hospital, S for social leave, D for destroyed, N for nausea or vomiting and A for absent. There is no single national list. Each provider sets its own key, prints it on the chart, and trains staff to use it the same way every time.

The short answer

A MAR chart records every medicine a person is prescribed and what happened at every scheduled time. A signature or initials means the dose was given. A code means it was not given, or was given differently, and the code says why. The codes matter because a MAR chart is the only real evidence that medicines were managed safely. If the key is unclear, if staff use the wrong letter, or if a box is left blank, the chart stops being evidence and becomes a question. The rest of this article walks through what each code means, what must be written alongside it, and how a manager checks the codes are being used honestly.

What is a MAR chart and what does MAR stand for?

MAR stands for medication administration record. Some people say MAR sheet, some say MAR chart, some say MARS chart. They all mean the same document. It is a grid. Down the side is every medicine the person takes, with the dose, the route and the times. Across the top are the days of the month. Each box where a medicine meets a day and a time is a record of one dose.

The MAR chart meaning in practice is simple. It is the account of what went into the person. It is not a prescription. It is not the care plan. It is the record of administration, and for that reason it is one of the first things an inspector or a pharmacist will pick up. A MAR chart example from a well-run home shows a full grid, every box filled, every code explained on the back or in the daily notes, and a printed key at the foot of the page.

The chart is usually produced by the community pharmacy that supplies the medicines, and it runs for a four-week cycle. The home is responsible for checking it against the prescription when it arrives, adding any changes made mid-cycle, and keeping it accurate.

At a glance: the common MAR chart codes

These are the codes I have seen most often across residential, nursing, learning disability and mental health services. Your own key may differ. The point of the table is to show what each code should mean and what should be written alongside it.

Why MAR chart codes vary by provider

There is no law that says R must mean refused. The Misuse of Drugs Regulations, the NICE guideline on managing medicines in care homes and the CQC guidance all require a clear, accurate record of administration. None of them prescribe a letter code. So each pharmacy and each provider has evolved its own key. One pharmacy uses F for refused. Another uses X for not given. A third has separate codes for refused and for spat out.

This is not a problem as long as three things are true. The key is printed on the chart or on a laminated sheet beside it. Every member of staff who signs the chart has been trained on that key. And the key does not change halfway through a cycle. Where it goes wrong is when a home changes pharmacy and the new charts arrive with a different key, or when an agency worker brings the codes from their last placement. That is when you find an O that was meant to be an R, and nobody can say which it was six weeks later.

If you run more than one home, standardise the key across the group. It makes audit simpler and it means a deputy covering another site does not have to relearn the alphabet.

Should medication refusal be recorded on a MAR chart?

Yes, every time, without exception. The refusal code is not an admission of failure. It is the record that the person exercised a choice, and that the home respected it. The chart is incomplete without it.

What sits behind the R is what an inspector will ask about. A refused dose should have a short note somewhere, either on the reverse of the chart or in the daily log, saying what was offered, how it was offered and whether it was offered again later. A person who refuses their morning tablets at eight and takes them happily at half past nine has not refused; they have been given late. A person who refuses three days running has a change in presentation that the GP needs to hear about.

For someone who lacks capacity to decide about a particular medicine, refusal opens a different question. A best interests decision under the Mental Capacity Act 2005 may be needed, and if the outcome is covert administration, that must be agreed with the prescriber and the pharmacist and written into the care plan. The R on the chart is the start of that process, not the end of it.

Omitted: the code that always needs a reason

O is the code most likely to hide a problem. Omitted means the dose was not given and the reason was not one of the specific codes. Sometimes the reason is good. The medicine was out of stock because the pharmacy delivered late. The GP had told the home to hold it pending a blood result. The person was nil by mouth before a procedure.

Sometimes the reason is not good. The trolley round ran out of time. The medicine could not be found. The worker was not sure of the dose and did not ask. All of these are medication errors and need to go through the incident process, not just sit on the chart as an O.

The rule I set in my own homes is that O is never used without a written reason and a name. If the person entering it cannot say why, they need to find out before they write anything. An unexplained O in a monthly audit is treated as a missed medication until proven otherwise. That sounds hard, but it is the only way to make the code honest.

Out of stock is an O with a story

If the reason is stock, the story must include when the pharmacy was called, what they said, and whether the GP was asked for an interim supply. A single missed dose of a laxative is one thing. A missed dose of an anti-epileptic or a Parkinson's medicine is a safeguarding concern and may need reporting.

Hospital, social leave and absent

H, S and A all say the person was not there to be given the dose. They are different, and the difference matters for stock and for safety.

H means in hospital. The code runs from the admission until the person returns. The chart should show the date of admission and the date of return, and there should be a record of what medicines went with the person and what came back. Discharge summaries change medicines more often than not, so a return from hospital always triggers a full check of the chart against the new prescription before the next dose is given.

S means social leave: out for the day with family, a weekend at home, a holiday. The record must show what was sent out, in what form, who took responsibility and what was returned. Sending a week of blister packs out with a relative and having three days' worth come back is a stock discrepancy that must be explained.

A is used in two different ways depending on the provider. Some use it for absent, meaning the person was out at the scheduled time and the dose was given later or not at all. Others use it for asleep. Because of that ambiguity, I prefer separate codes. If someone was asleep, the note should say whether they were woken, and if not, why not, and whether the dose was given on waking or missed.

Destroyed, dropped and returned

D usually means the dose was destroyed. That covers a tablet dropped on the floor, a capsule spat out, a liquid dose spilt. The chart records that the dose was not given and the note records what was done with it. A dropped tablet from a blister pack is usually disposed of in the pharmaceutical waste bin and a replacement given from stock, which then needs recording as a second dose given, not a repeat of the first.

For controlled drugs, D has extra weight. A dropped or refused controlled drug dose must be destroyed in the presence of a witness and recorded in the CD register with both signatures. The MAR code alone is not enough. The same applies to a part dose of a liquid controlled drug that was drawn up and not used.

Some providers use a separate code for returned to pharmacy, so that the chart shows why a stock count is lower than expected. If you do not have that code, the returns book does the job, but the audit trail has to connect.

Nausea, vomiting and the clinical codes

N is for nausea or vomiting. It matters because a dose that was given and then vomited within a short time may not have been absorbed, and a dose that was not given because the person was vomiting has been missed. The note must say which it was and when. For most medicines the answer is to seek advice and not to repeat the dose without it. For a few, such as anti-epileptics or insulin, it needs a clinical decision quickly.

Other clinical codes vary. Some charts have a code for withheld on clinical grounds, used when a nurse holds a dose because the observations are outside the parameters on the chart, such as a low pulse before a beta blocker or a low blood sugar before insulin. This is not an omission and not a refusal. It is a decision, and the record needs the observation, the parameter and the name of the person who made the call.

Whatever the letter, the principle is the same. A clinical code records a clinical decision, and a clinical decision has a decision-maker and a reason.

Codes for PRN and variable doses

PRN medicines, given when required, have a different pattern on the chart. Most of the boxes are empty, because most of the time the medicine is not needed. That is correct, but an empty box on a regular medicine means missed and an empty box on a PRN medicine means not needed, and that contradiction is where charts go wrong.

The cleaner approach is a code for PRN not required, or a line drawn through, so that every box has something in it. When a PRN dose is given, the chart shows the time, the dose, the reason and the outcome, and for variable doses such as one or two tablets, it shows exactly how many were given. Two tablets recorded as one dose is a stock discrepancy waiting to happen.

Every PRN medicine should have a written protocol behind it. The protocol says when to give it, how much, how often, what to try first and when to escalate. Without it, the code on the chart tells you the medicine was given but not whether it was the right call. There is a separate guide to writing them at PRN medication protocols.

Self-administration and covert administration

Some people manage some or all of their own medicines. That is their right, and it should be supported where a risk assessment shows it is safe. On the chart, a self-administered medicine is still listed but the box shows a code, often SA, rather than a staff signature. The home's job is to check the person is taking it, to keep the risk assessment reviewed, and to record that check.

Covert administration is the opposite situation. A person who lacks capacity to consent to a medicine may, following a best interests decision, be given it hidden in food or drink. Some providers use a code on the chart for this. Others prefer the chart to show a normal signature with the care plan holding the covert decision. Either is acceptable as long as the decision is documented, the pharmacist has confirmed the medicine can be crushed or mixed, and the arrangement is reviewed. What is not acceptable is covert administration with no decision behind it. That is a safeguarding matter.

The difference between a code and a note

A code is a single letter. It cannot carry the story. That is why every code except a routine signature needs a note somewhere that says what happened and who decided. Where the note lives depends on your system. On paper charts, the reverse of the MAR is the usual place. In an electronic system, the note is attached to the entry itself.

The test I use is whether a stranger could reconstruct the event. If the chart says R at 08:00 on the 14th, could a pharmacist doing the quarterly review find out what was offered, whether it was re-offered, and what the person said? If the chart says O on the 20th, could I as the manager find out why, without asking the worker who wrote it? If the answer is no, the record is not good enough.

Notes should be factual and short. Not: refused, uncooperative. Instead: offered tablets in a pot at 08:05, said she did not want them, offered again at 09:30 with a drink, took them. That second note tells the reader something. The first tells them nothing and blames the person.

Blank boxes and missed medication

A blank box is the worst entry on a MAR chart, because it is not an entry. It could mean the dose was given and not signed. It could mean it was not given and not coded. Nobody knows, and six weeks later nobody will remember. Every blank box in a monthly audit is a missed medication until the worker who was on duty can account for it, and if they cannot, it goes through the error process.

Gaps happen for predictable reasons. The worker was interrupted mid-round. Two people shared a round and each thought the other had signed. The chart was in the wrong place. A new chart started mid-month and the old one was not carried across. All of these are system problems, not individual ones, and the fix is in the system: one person per round, a check at the end of each round, and a handover that includes the chart.

Where a home has repeated gaps, the honest position is that it does not know whether people are getting their medicines. That is what an inspector will conclude, and they will be right to. Electronic systems remove the blank box entirely, because the entry cannot be closed without a signature or a code. The guide to what eMAR is explains how that works.

How to set up your MAR chart code key

If your key has grown by accident, or you are changing pharmacy, it is worth rebuilding it deliberately. This is the procedure I would follow.

1. Ask your pharmacy for the codes printed on their standard chart, and use those as the base so the printed chart and your policy agree.
2. Decide on separate codes for absent and asleep, and for refused and destroyed, so that no letter has two meanings.
3. Add a code for PRN not required so that no box on the chart is ever legitimately blank.
4. Write a one-line definition for each code and a one-line rule for what must be recorded alongside it.
5. Put the key on every chart, on the trolley, and in the medicines policy, and date it.
6. Train every member of staff who administers medicines, including bank and agency, and keep a signed record of that training.
7. Set a start date and change every chart on the same day. Do not run two keys at once.
8. Audit the first month closely and correct misuse straight away, before it becomes habit.

Training staff to use codes consistently

Consistency is the whole game. Ten workers using the same code the same way produce a chart that can be read. Ten workers each with their own understanding produce noise. Training for medicines administration should include a session on the code key, with real examples: here is a chart, here is what happened, what do you enter and what do you write?

Competency assessment should include the codes too. It is not enough to watch someone administer a dose correctly. Watch them handle a refusal, an out-of-stock, a dropped tablet, and see what they record. That is where most errors in the record happen, and it is where an assessor learns whether the worker understands what the chart is for.

Refresh it when the pharmacy changes, when the key changes, and whenever an audit shows a pattern of misuse. A short huddle at handover with the chart in hand is more effective than a written memo that nobody reads.

Reading a MAR chart for patterns

Once the codes are reliable, the chart becomes a tool rather than a chore. A run of R codes on the evening dose and none in the morning tells you something about how the person feels at night, or who is on duty at night. A run of N codes tells you a person is unwell and the GP may not know. A cluster of O codes on a Sunday tells you about your weekend staffing or your stock process.

I look at the chart as a picture, not a list. Which medicines are never coded? Which are coded every week? Are the codes clustered by time, by day, by worker? A resident who has refused antipsychotic medicine four times this month needs a review, and possibly a capacity assessment, and the chart is the evidence that starts the conversation.

Electronic systems make this easier because they can filter by code and by person, but a paper chart read carefully once a month will show the same things. The point is to read it.

Codes on paper versus codes on eMAR

On a paper chart the code is whatever the worker writes. If they are unsure, they may leave it blank or guess. On an electronic MAR, the code is chosen from a list, the note is usually mandatory for anything other than given, and the entry is time-stamped. That does not make the record true, but it makes it complete, and completeness is where paper fails most often.

Electronic systems also carry the key with them. There is no laminated sheet to go missing, and no new pharmacy chart with a different alphabet. If the provider has set up the codes properly, an agency worker on their first shift sees the same options as the deputy manager. In practice, an eMAR with rounds by resident, which is how Kiwi runs its medicine rounds, prompts the worker through every scheduled dose, will not let a box close without an entry, and flags a refusal or an omission to the manager the same day rather than at the end of the month. Whether you are on paper or electronic, the audit questions in the next section are the same. The comparison in eMAR versus paper MAR goes into the trade-offs.

Auditing MAR chart codes each month

A monthly MAR audit is the manager's check that the record is honest. It does not have to be long. For each chart, run through this list.

• Every box has a signature or a code. Count the blanks and account for each one.
• Every code other than a signature has a note that explains it.
• Every O has a reason and a name. Any O without a reason is logged as a missed dose.
• Every R for a critical medicine, or any medicine refused three times or more, has been reported to the GP.
• Every D for a controlled drug has a matching entry in the CD register with a witness.
• Every H and S has a record of what left the building and what came back.
• Every PRN given has a time, a dose, a reason and an outcome, and matches the protocol.
• The chart matches the current prescription, including any mid-cycle changes.
• Stock counts for at least two medicines per chart reconcile with the doses recorded.

Write the findings down, date them, and record the action taken. An audit with no actions is not an audit; it is a signature. A system that keeps the audit trail in one place, such as the audit and evidence tools built into a care management platform, makes the monthly check quicker, but the questions are the same on paper.

Codes and the medication error process

Some codes are records of something normal. A refusal is a choice. Social leave is a life. Other codes are records of an error, and the code on the chart is only the first step. A dose omitted because the stock ran out, a dose given late enough to matter, a dose destroyed because the wrong tablet was popped, all of these need an incident report, a look at what caused it, and a note of what will change.

The link between the chart and the incident system is where many homes lose the thread. The chart shows O, the daily notes show nothing, and the incident log is empty. When the inspector asks how many medication errors there were last quarter, the honest answer is that the home does not know. Set the rule that any O or D that was not planned is an incident, and check in the audit that the numbers match.

Errors are not a mark against a home. A home with a clean incident log and a chart full of unexplained codes is the one that worries me, and it worries inspectors too. A separate incident module, or a simple log, is fine; what matters is that the chart and the log agree.

Codes and the person's care plan

The MAR chart records what happened. The care plan records what should happen and why. The two must agree. If the care plan says a person likes their tablets in yoghurt at breakfast and the chart shows refusals every morning, someone is not reading the plan. If the chart shows a person self-administering their inhaler and the care plan has no risk assessment for it, the plan is out of date.

Every code pattern that lasts more than a week or two should prompt a look at the plan. Repeated refusals may mean the medicine needs reviewing, or the time needs changing, or the person needs a different explanation. Repeated N codes may mean the medicine is causing the nausea. Repeated A codes for asleep may mean the medicine round is too early for that person and the plan should say so.

A care plan with a medicines section that is reviewed alongside the chart is what turns codes into care. Without that link, the chart is a record of problems that nobody is solving.

Codes for people who lack capacity

In learning disability and mental health services, and in nursing homes with residents living with dementia, a large proportion of the people on the chart may lack capacity to make some decisions about their medicines. That does not change the codes. It changes what has to sit behind them.

A refusal from someone who lacks capacity is still recorded as R. But the note, and the care plan, must show that a capacity assessment has been done for that decision, that a best interests decision has been made about how to respond, and that the least restrictive option has been chosen. For someone under a Deprivation of Liberty Safeguards authorisation, or under a community treatment order, the conditions of that authorisation may say something specific about medicines, and the home must know what.

The mistake is to treat capacity as a single yes or no. A person may be able to decide about paracetamol and not about an antipsychotic. The record has to be that specific. The Mental Capacity Act Code of Practice sets out the steps, and the care plan should show them.

Common mistakes

• No key on the chart. The codes exist in someone's head and change with the pharmacy or the agency.
• One letter, two meanings. A used for both absent and asleep, or D used for both destroyed and declined.
• O with no reason. Omitted becomes a dumping ground for every dose that was not given, and the real missed doses hide inside it.
• Blank boxes left to the end of the month. By then nobody remembers, and every blank is a missed dose that cannot be explained.
• PRN boxes left empty. Nobody can tell whether the medicine was not needed or the entry was forgotten.
• Refusals not reported. The chart shows a fortnight of R codes for an anticoagulant and the GP has not been told.
• Codes never read. The chart is filed at the end of the cycle without anyone looking for patterns.
• Codes without care plan changes. The same problem recurs every month because the plan was never updated.

What good looks like on inspection day

When an inspector or pharmacist asks for the MAR charts, this is what I want them to find. Every chart has a printed key, and the key matches the medicines policy. Every box for the current cycle has a signature or a code. Every code has a note, and the note has a name. The refusals for one resident have led to a GP review, and the review is in the care plan. The omissions for last month were all out-of-stock events, each was logged as an incident, and the pharmacy was contacted each time, with a record of the call.

The controlled drugs register matches the chart for every D. The stock count for the two medicines the inspector picks reconciles to the dose. The audit for last month is signed, dated, and has three actions, two of which are closed. The staff member the inspector asks can explain what O means and what she would write alongside it, without looking at the sheet.

None of this needs a perfect chart. It needs an honest one, with a manager who can show they read it. If you want to see how an electronic chart handles codes, notes and audit in one place, book a demo and bring your current key with you. That is the inspection-ready evidence: not that nothing went wrong, but that everything that went wrong was seen and dealt with.

Final conclusion

MAR chart codes are a small thing that carries a lot of weight. They vary by provider, and that is fine, as long as your key is printed, trained and consistent. Every code needs a note, every O needs a reason, every blank is a missed dose until proven otherwise, and every pattern needs a look at the care plan. Get those habits in place and the chart stops being a form to fill in and becomes the record that protects the people in your care and the people who look after them.

Frequently asked

What do the codes on a MAR chart mean?

They are short letters that record why a dose was not given in the normal way. Common examples are R for refused, O for omitted, H for in hospital, S for social leave, D for destroyed, N for nausea or vomiting and A for absent or asleep. There is no national standard, so always check the key printed on your own chart.

Should medication refusal be recorded on a MAR chart?

Yes, every time. Enter the refusal code and write a short note saying what was offered, how, and whether it was offered again. If the medicine is critical or the refusal repeats, tell the GP. For someone who lacks capacity, a refusal may also need a best interests decision.

What is the difference between refused and omitted on a MAR sheet?

Refused means the person was offered the dose and declined it. Omitted means the dose was not given for another reason, such as being out of stock or withheld on clinical advice. Omitted always needs a written reason and a name, because it is the code most likely to hide a missed medication.

What should I do about a blank box on a MAR chart?

Treat it as a missed medication until it can be explained. Ask the worker who was on duty as soon as possible, record what you find, and if the dose was not given, put it through the medication error process. Repeated blanks are a system problem and need a change to how rounds are run and checked.

Do MAR chart codes have to be the same in every care home?

No. Codes vary by pharmacy and by provider. What matters is that the key is printed on the chart, staff are trained on it, no letter has two meanings, and the key does not change mid-cycle. Providers with more than one home should use one key across the group.

How often should a manager audit MAR chart codes?

Monthly, at the end of each cycle, and more often if an audit shows problems. Check that every box has an entry, every code has a note, every omission has a reason, refusals of critical medicines have been reported, and controlled drug codes match the register. Record the findings and the actions.

Are MAR chart codes different on an electronic MAR?

The meanings are the same but the system enforces them. Codes are chosen from a list, a note is usually required for anything other than given, entries are time-stamped, and a box cannot be closed without an entry, so blanks disappear. Managers can also filter by code to spot patterns quickly.

Sources

• NICE guideline SC1 Managing medicines in care homes
• NICE guideline NG67 Managing medicines for adults receiving social care in the community
• CQC: medicines guidance for adult social care, including administration records
• Royal Pharmaceutical Society: The handling of medicines in social care
• Misuse of Drugs Regulations 2001
• GOV.UK: Mental Capacity Act 2005 Code of Practice
• Skills for Care: medication competency and the Care Certificate standard on medication