One wrong letter on a prescription can kill someone. It’s not science fiction-it’s a daily risk in hospitals, clinics, and pharmacies across the world. In 2022, a pharmacist in Brisbane caught an order for MS 10 mg SC. At first glance, it looked like morphine sulfate. But if misread as MgSO4-magnesium sulfate-it could have triggered cardiac arrest in a patient with kidney failure. The error was caught in time. But how many aren’t?
These aren’t typos. They’re system failures. For decades, doctors, nurses, and pharmacists have used shorthand to save time. But when ‘QD’ means once daily, and someone reads it as ‘QID’ (four times daily), the result isn’t a minor mistake-it’s a drug overdose. The same goes for ‘U’ for units. That tiny letter looks like a zero or a four. One pharmacist in the U.S. reported a patient received 10 times the insulin dose because ‘10 U’ was read as ‘100’.
Why These Abbreviations Are So Dangerous
It’s not about laziness. It’s about ambiguity. The human brain fills in gaps. When you see ‘QOD’, your mind might jump to ‘every day’ instead of ‘every other day’. ‘BIW’-twice weekly-gets mistaken for ‘twice daily’ because ‘W’ isn’t obvious. In a fast-paced ER, or when handwriting is smudged, those tiny letters become landmines.
The Joint Commission and the Institute for Safe Medication Practices (ISMP) have been warning about this since 2001. Their ‘Do Not Use’ list isn’t a suggestion. It’s a safety rule. And it’s backed by hard data: 43.1% of all abbreviation-related medication errors come from just one-‘QD’. That’s more than half of all abbreviation mistakes. And ‘MS’? It’s the most confused drug abbreviation. Morphine sulfate versus magnesium sulfate. One calms pain. The other stops your heart if given to the wrong patient.
The Top 5 Abbreviations That Kill
- QD - Means once daily. But it’s read as QID (four times daily) or QOD (every other day). Result? Overdose or underdose. Always write ‘daily’.
- U - Stands for units. Looks like a zero, a four, or even ‘cc’. Insulin errors from this alone cause hundreds of deaths each year. Write ‘units’ in full.
- MS or MSO4 - Morphine sulfate. Easily confused with MgSO4 (magnesium sulfate). The difference? One is for pain. The other is for seizures or preeclampsia. Mix them up, and you risk cardiac arrest.
- SC or SQ - Subcutaneous. But ‘SQ’ looks like ‘5 every’ in messy handwriting. ‘SC’ can be mistaken for ‘SL’ (sublingual). Always write ‘subcutaneous’.
- IU - International unit. Looks like ‘IV’ (intravenous) or ‘10’. Giving an injection labeled ‘IU’ when it should be oral? That’s a dangerous mix-up.
And don’t forget ‘cc’. It’s been banned for over 20 years. It means cubic centimeters. But people read it as ‘u’ for units. So ‘5 cc’ becomes ‘5 units’-a fatal error with insulin or heparin. Use ‘mL’ instead. Always.
What About Drug Names?
Abbreviating drug names is even riskier. ‘AZT’ for zidovudine? Someone might read it as azathioprine (an immunosuppressant) or aztreonam (an antibiotic). Different diseases. Different treatments. Same letters. Big difference.
‘TAC’ for triamcinolone cream? Sounds like ‘Tazorac’-a different acne medication. A patient gets the wrong cream for eczema. Skin gets worse. Infection sets in. This happened in a 2017 case documented by ISMP. The handwriting was sloppy. The result? Months of unnecessary suffering.
And ‘DTO’-diluted tincture of opium? Sounds like morphine sulfate. Both are opioids. But dosing is completely different. One is for diarrhea. The other is for severe pain. Confuse them? You could overdose someone on a drug meant for mild symptoms.
Technology Isn’t the Full Fix
Electronic health records (EHRs) were supposed to solve this. And they did-sort of. A 2021 study showed EHRs cut abbreviation errors by 68%. But 12.7% of errors still happened. Why? Because doctors still type free-text notes. ‘Give MS 10 mg SC’-typed, not selected from a dropdown. The system doesn’t always flag it.
Some hospitals now use AI tools that auto-correct ‘QD’ to ‘daily’ or block ‘U’ from being typed. Epic Systems rolled this out to 72% of U.S. hospitals by late 2023. But in small clinics, community pharmacies, and rural areas? Many still use old systems-or paper. And handwritten prescriptions? They’re still common in Australia, especially in aged care homes and outback clinics.
The real problem isn’t tech. It’s culture. A 2022 survey found that 43.7% of doctors over 50 still use banned abbreviations-even when their hospital bans them. They’ve done it for 30 years. ‘QD’ is just faster. ‘U’ is what they learned in med school. Changing habits is harder than changing software.
What Works: Real Solutions
Successful hospitals don’t just ban abbreviations. They train, enforce, and support.
- Hard stops in EHRs - If someone types ‘QD’, the system won’t let them submit. It forces them to pick ‘daily’ from a menu.
- Education with real examples - Instead of a 10-slide PowerPoint, show real cases. ‘This is the order that almost killed a 72-year-old.’
- Pharmacist feedback loops - When a pharmacist catches an error, they flag it to the prescriber. Not as punishment. As learning.
- Standardized templates - Pre-filled order sets for common conditions (pain, diabetes, infection) remove the need to type abbreviations at all.
Mayo Clinic cut abbreviation errors by 92% using this combo. They didn’t just say ‘don’t use QD’. They built the system to make the right choice the only choice.
What You Can Do
If you’re a patient: Always ask. If your prescription says ‘MS’, ask: ‘Is that morphine or magnesium?’ If it says ‘U’, ask: ‘Is that units?’ If it says ‘QD’, ask: ‘Once a day, right?’ Don’t assume. Don’t be shy. Your life could depend on it.
If you’re a healthcare worker: Use the full word. Always. Even if it takes 2 extra seconds. That’s the cost of safety. If you see someone using ‘SC’ or ‘U’ or ‘QOD’-politely correct them. Show them the ISMP list. Bring it up at your next team huddle.
If you’re a manager: Don’t just post the list on the wall. Integrate it into your EHR. Train new staff on day one. Audit prescriptions monthly. Reward teams that catch errors before they happen.
The Bigger Picture
This isn’t just about paperwork. It’s about trust. When a nurse gives a drug based on a scribbled note, they’re trusting a system that’s broken. When a pharmacist fills a bottle labeled ‘DTO’, they’re trusting a doctor who doesn’t know better.
The fix is simple: write it out. Say it clearly. Check it twice. The data is clear: eliminating these abbreviations prevents 37% of all medication errors. That’s tens of thousands of lives saved every year in the U.S. alone. In Australia, where the Australian Commission on Safety and Quality in Health Care adopted similar rules in 2022, the same logic applies.
There’s no excuse anymore. We’ve known what to do for over 20 years. We have the tools. We have the evidence. What we need now is the will.
Next time you see a prescription with ‘QD’, ‘U’, or ‘MS’-stop. Don’t guess. Don’t assume. Ask. Correct. Save a life.