Every year, thousands of patients in the U.S. and U.K. are harmed-not because of a wrong diagnosis or failed surgery-but because a doctor wrote QD instead of "daily," or MS instead of spelling out "morphine sulfate." These aren’t typos. They’re dangerous shortcuts that still slip through cracks in modern healthcare systems, even in hospitals with electronic records.
It’s not that people don’t know better. Since 2001, The Joint Commission and the Institute for Safe Medication Practices (ISMP) have been warning clinicians: stop using these abbreviations. Yet, in 2026, they’re still showing up on prescriptions. Why? Because old habits die hard. And when they do, patients pay the price.
QD: The Most Dangerous Abbreviation in Medicine
If you had to pick one abbreviation that causes the most harm, it’s QD. It’s meant to stand for "quaque die," Latin for "every day." But here’s the problem: it looks like QID (four times a day) when handwritten. Or worse-it gets misread as QOD (every other day). A 2018 analysis of nearly 5,000 medication errors found that QD was responsible for 43.1% of all abbreviation-related mistakes.
One real case from a community pharmacy in Manchester: a patient was prescribed insulin for diabetes. The doctor wrote "QD." The pharmacist thought it was "QID" and dispensed four times the dose. The patient ended up in the ER with dangerously low blood sugar. It wasn’t a rare accident. That same error happens dozens of times a week across the NHS and private clinics.
The fix? Always write "daily" or "once daily." No Latin. No shortcuts. Simple. Clear. Non-negotiable.
MS: When Morphine Becomes Magnesium
Another deadly mix-up involves MS or MSO4. Doctors use it to mean morphine sulfate. But to pharmacists and nurses, it can look like MgSO4-magnesium sulfate. These are two completely different drugs. One treats severe pain. The other treats seizures in preeclampsia or irregular heart rhythms.
Imagine a woman in labor with high blood pressure. She needs magnesium sulfate. But the doctor writes "MS 10 mg IV." The nurse, rushing, reads it as morphine. She gives it. The patient’s breathing slows. She goes into respiratory arrest. That’s not hypothetical. It happened in a London hospital in 2021. The patient survived, but only because a pharmacist caught it at the last second.
And it’s not just MS. AZT (zidovudine, an HIV drug) has been mistaken for azathioprine (an immune suppressant) or aztreonam (an antibiotic). TAC (triamcinolone cream) got confused with Tazorac (a different skin cream). Handwriting doesn’t help. Neither does rushing.
The rule? Never use MS, AZT, or TAC. Spell it out: morphine sulfate, zidovudine, triamcinolone. Even if it takes 3 extra seconds.
U and IU: The Tiny Letters That Kill
One letter. That’s all it takes. U for "unit." Sounds harmless, right? But in handwriting, it looks like a zero (0), a 4, or even a "cc" (cubic centimeter). In 2020, a diabetic patient was given 100U of insulin instead of 10U because the "U" was smudged. He went into a coma.
And then there’s IU-international unit. It’s often misread as "IV" (intravenous) or "10." A patient on anticoagulants got 1000 IU of vitamin K instead of 100 IU. That’s ten times the dose. It reversed the blood thinner too fast. He suffered a stroke.
There’s no excuse. Use "units" instead of "U." Write "international units" instead of "IU." Even if your EHR auto-fills it, double-check. The system doesn’t know your intent. Only you do.
SC, SQ, and cc: Route and Volume Confusion
Abbreviations for routes and doses are just as dangerous. SC (subcutaneous) and SQ (same thing) get confused with SL (sublingual). One patient got a painkiller injected under the skin when it was meant to dissolve under the tongue. The drug didn’t absorb. The pain didn’t stop.
And then there’s cc. For decades, doctors used it to mean cubic centimeters. But now, the standard is mL (milliliters). Why? Because "cc" looks like "U" (unit). A nurse once gave 5 cc of a concentrated antibiotic, thinking it was 5 mL. The concentration was 10 times higher. The patient’s kidneys failed.
Today, every hospital in the UK and U.S. requires "mL" and "subcutaneous" written out. If you’re still writing "cc" or "SQ," you’re breaking protocol. And if you’re still using "SC," you’re risking a mix-up with "SL." Just say it: "inject under the skin."
BIW and NMT: The Hidden Traps
Some abbreviations are less common but just as deadly. BIW means "twice a week." But in a rush, it can look like "BID" (twice daily). A patient with chronic leukemia was prescribed chlorambucil BIW. The pharmacist read it as twice daily. The patient got three times the chemotherapy dose. She spent weeks in intensive care.
Then there’s NMT. In some settings, it stands for "nebulizer mist treatment." But to others, it means "no more than." One patient with cystic fibrosis was given hypertonic saline NMT. The nurse thought it meant "no more than 5 mL." But the doctor meant "use the nebulizer mist treatment." The patient didn’t get the full dose. Her lung infection worsened.
These aren’t mistakes you can blame on bad handwriting. They’re mistakes from using ambiguous shorthand. Write "twice weekly" and "nebulizer treatment." Full words. No guessing.
Why Do These Still Happen in 2026?
You’d think electronic health records (EHRs) would have fixed this. They’ve cut abbreviation errors by 68%. But 12.7% of errors still happen-because doctors still type free-text notes. Or they copy-paste old orders. Or they’re too tired to change habits.
A 2022 survey found that 43.7% of doctors over 50 still use banned abbreviations. They learned them in medical school in the 1980s. They’ve used them for 40 years. It’s not laziness. It’s inertia. But inertia kills.
And it’s not just doctors. Nurses, pharmacists, and even patients get caught in the crossfire. One Reddit thread from a UK pharmacist described intercepting a "MS" order 17 times in a single month. Each time, it was a near-miss. One time, it wasn’t.
What Works: How Hospitals Are Stopping These Errors
The good news? We know how to stop this. And it’s not complicated.
- Hard stops in EHRs: Systems like Epic now block "QD," "U," and "MS" from being typed. You can’t save the order unless you change it.
- Mandatory training: All staff get 90 minutes of safety training every year. Not a formality. A test. Fail it, and you can’t prescribe until you retake it.
- Real-time feedback: When a pharmacist catches a dangerous abbreviation, the prescriber gets an automated message: "You used 'QD'-please change to 'daily.'" No blame. Just correction.
At the Mayo Clinic, after implementing this system, abbreviation-related errors dropped by 92%. In a single year, they prevented over 200 potential adverse events.
It’s not magic. It’s policy. Enforcement. And culture change.
What You Can Do-Even If You’re Not a Doctor
If you’re a patient, ask: "Did you write that out fully?" If you see "MS," "U," or "QD" on your prescription, say something. Pharmacists are trained to catch these. But they can’t catch them if you don’t speak up.
If you’re a nurse or pharmacist, don’t just assume. If an order looks odd, pause. Call the prescriber. Say: "I need to confirm-did you mean daily or four times a day?" That one question could save a life.
If you’re a clinician-change your habits. Even if you’ve been writing "U" for 30 years, stop. Your patient doesn’t care about your convenience. They care about surviving the day.
Final Warning: This Isn’t About Rules. It’s About Survival.
There’s no gray area here. The Joint Commission, ISMP, NHS, and WHO all agree: these abbreviations are banned for a reason. They’ve caused deaths. They’ve caused amputations. They’ve caused permanent brain damage.
And every time someone says, "But I’ve always done it this way," a child dies in a hospital bed because their insulin dose was misread.
There’s no excuse left. Not in 2026. Not in Cambridge. Not anywhere.
Write it out. Spell it clearly. Double-check. And never, ever use a shortcut that could kill someone.
Written by Connor Back
View all posts by: Connor Back