Dangerous Medical Abbreviations That Cause Prescription Errors

Every year, thousands of patients are harmed-not because of the medicine they’re taking, but because of how it was written down. A tiny abbreviation on a prescription can mean the difference between healing and hospitalization. In 2023, a pharmacist in Perth intercepted an order for MS 10 mg. The doctor meant morphine sulfate. The nurse read it as magnesium sulfate. It was a near-fatal mix-up. This isn’t rare. It’s predictable. And it’s entirely preventable.

Why These Abbreviations Are Deadly

Medical abbreviations aren’t shortcuts. They’re landmines. What looks like a quick way to write a prescription often becomes a dangerous miscommunication. The Joint Commission and the Institute for Safe Medication Practices (ISMP) have been warning about this for over 20 years. Their Do Not Use list isn’t a suggestion-it’s a safety rule. And yet, errors still happen every day.

The most dangerous abbreviation? QD. It’s meant to mean “once daily.” But when handwritten, it looks like QOD (every other day) or even qid (four times daily). A 2018 analysis of nearly 5,000 medication errors found that QD was involved in 43% of all abbreviation-related mistakes. One patient got a daily dose of chemotherapy meant to be given every other day. They ended up in intensive care.

Then there’s U for “unit.” It’s been mistaken for a zero, a four, or even the letter “V.” A diabetic patient was given 100 units of insulin instead of 10 because the “U” looked like a “0.” That’s not a typo. That’s a death sentence.

And don’t forget cc. It stands for cubic centimeters. But pharmacists know it’s often confused with “u” for units. So when a doctor writes “5 cc,” a pharmacist might think it’s “5 units.” In one case, a child was given a lethal dose of epinephrine because “5 cc” was misread as “5 U.”

The Most Common Killer Abbreviations

Some abbreviations are so dangerous, they’ve been banned in hospitals across Australia, the U.S., Canada, and the UK. Here are the top offenders-and what to write instead:

• MS or MSO4 → Always write “morphine sulfate.” Never use “MS.” It’s too easily confused with MgSO4 (magnesium sulfate), which is used for seizures and preeclampsia. Mixing them up can cause respiratory arrest.
• QD, QOD, BIW → Write “once daily,” “every other day,” or “twice weekly.” No shortcuts. Handwriting can blur letters. A computer can’t guess what you meant.
• U → Write “unit.” Always. Even if it takes an extra second.
• IU → Write “international unit.” It’s been mistaken for “IV” (intravenous) or “10.” One patient received an IV bolus instead of an oral dose because of this.
• SC or SQ → Write “subcutaneous.” “SC” has been read as “SL” (sublingual), and “SQ” has been mistaken for “5 every.”
• TAC → Write “triamcinolone.” It’s been confused with “Tazorac,” a completely different skin medication. A patient got the wrong cream and developed severe skin damage.
• DTO → Write “diluted tincture of opium.” It’s been mistaken for morphine sulfate. Both are opioids, but dosing is wildly different.
• AZT → Write “zidovudine.” It’s been confused with azathioprine (an immune suppressant) or aztreonam (an antibiotic). The wrong drug can cause bone marrow failure.
• NMT → Write “nebulizer mist treatment” or “no more than,” depending on context. Ambiguity kills.

Why Do Doctors Still Use Them?

You’d think after two decades of warnings, everyone would stop. But they don’t. A 2022 survey found that 44% of physicians over 50 still use banned abbreviations. Why? Habit. Tradition. Speed. Some say they’ve used “QD” for 30 years and it’s never caused a problem. But that’s not luck. It’s roulette.

Older doctors were trained in an era of handwritten charts. Abbreviations saved time. Now, we have electronic systems that can flag errors in real time. But if the prescriber types “MS” anyway, the system can’t always stop it. And many still dictate notes or scribble on paper pads.

It’s not just doctors. Nurses, pharmacists, and even patients sometimes misread what’s written. One Reddit thread from a pharmacist described catching 12 dangerous abbreviations in a single week. Over 80% of the comments were from other pharmacists saying, “I’ve seen that too.”

How Hospitals Are Fixing This

The good news? We know what works.

Hospitals that use electronic health records (EHRs) with hard stops have cut abbreviation errors by over 90%. A hard stop means the system won’t let you submit the order unless you fix it. If you type “QD,” it pops up: “Please write ‘once daily.’”

Mayo Clinic implemented this in 2020. They added mandatory training, real-time alerts, and penalties for repeated violations. Within 18 months, abbreviation-related errors dropped by 92%. That’s not just numbers. That’s lives saved.

But it’s not just about technology. It’s about culture. One pharmacy in Perth started a “No Abbreviations” campaign. They printed posters with the banned list and gave out stickers that said “Write it out.” Within six months, error reports dropped by 78%.

Even small clinics can do this. All it takes is a policy, a reminder, and the will to change.

What You Can Do

You don’t have to be a doctor or pharmacist to help. If you’re a patient:

• Always ask: “Is this written out fully? No abbreviations?”
• If you’re handed a prescription with “MS,” “U,” or “QD,” ask the pharmacist to confirm what it means.
• Keep a list of your medications with full names and dosages. Show it to every provider.

If you’re a healthcare worker:

• Use the full word. Always.
• Don’t assume someone else knows what you meant. Write it clearly.
• Report near-misses. If you catch an error, tell your team. That’s how systems improve.

There’s no excuse anymore. We have the tools. We have the data. We know what kills. The only thing left is to stop doing it.

What’s Changed in 2024

The ISMP updated their list in January 2024. They added 17 new dangerous abbreviations-mostly for HIV medications like DOR, TAF, and TDF. These were once considered safe because they’re used in specialized clinics. But now, more patients are taking them in community pharmacies. And mistakes are rising fast.

AI tools are now scanning EHRs in real time. Epic Systems, one of the biggest health record platforms, rolled out automatic detection for banned abbreviations to 72% of U.S. hospitals by late 2023. It flags “U” and “MS” as soon as they’re typed. But it’s not perfect. If a doctor types “TAF” and means “tenofovir alafenamide,” but the system thinks it’s “triamcinolone,” it’s still a risk.

The future? Voice recognition. Soon, when a doctor says “morphine sulfate,” the system will auto-fill the full term. No typing. No abbreviations. No room for error.

Why This Matters in Australia

Australia’s Safety and Quality Health Care Commission adopted the same standards in 2022. Hospitals here are required to follow the “Do Not Use” list. But community pharmacies and private clinics? They’re still catching up.

A 2023 study found that 64% of outpatient medication errors in Australia still involved dangerous abbreviations. That’s not a small number. That’s a crisis waiting to happen.

It doesn’t matter if you’re in Perth, Sydney, or a remote town. A misread abbreviation doesn’t care where you live. It only cares if someone reads it wrong.

Final Thought

Medicine is complex. But safety doesn’t have to be. Writing “once daily” instead of “QD” takes two seconds. Saying “morphine sulfate” instead of “MS” takes one extra breath. That’s all it takes to save a life.

There’s no glory in using abbreviations. There’s no prestige in being fast. There’s only responsibility. And responsibility means writing clearly-every single time.