13 Nursing Myths You Probably Fell For

William Kelly, MSN, FNP-C

Updated June 2026 · Medically reviewed for nurses

13 min read

Not everything you learn on the job is factual, and there are many nursing myths still commonly believed and "passed on" today. Some are rooted in truth; others have no real evidence behind them.

There's nothing more embarrassing than learning something, teaching it to others, and then realizing it isn't accurate. You may know some of these, but there are common myths you might not be aware of — so read all 13.

1. Letting Blood Tubes Sit Causes Hemolysis

A common myth is that "leaving blood tubes sit too long causes hemolysis." That's not true. When blood hemolyzes, the red cells lyse and release their intracellular contents, disrupting lab values — falsely elevating potassium (intracellular K+ is much higher than extracellular), as well as magnesium, phosphorus, liver enzymes, ammonia, and the anion gap, while falsely lowering RBCs, hematocrit, PTT, and more.

Hemolysis actually occurs from damage to red cells, usually during the draw due to collection technique. True causes include:

Blood drawn from IVs is much more likely to hemolyze; a site with great blood return and large veins helps. That's one reason the AC is a great choice for new ER IVs — great blood return. As it turns out, while sitting too long won't cause hemolysis, it can alter results depending on the tube and test. Tubes left at room temperature stay accurate for roughly: CBC up to 24 hrs; CMP should be centrifuged within 2 hrs for accurate glucose and potassium; PT/PTT up to 2 hrs if on heparin, otherwise 4 hrs; D-dimer up to 8 hrs.

2. The MONA Myth

We're taught the acronym MONA for suspected cardiac chest pain — Morphine, Oxygen, Nitroglycerin, Aspirin. It's not completely wrong, but it's an oversimplification, and sometimes these can actually harm the patient.

Oxygen

Don't apply oxygen to every chest-pain patient, even if you suspect a heart attack. First check the pulse ox and apply oxygen only if SpO2 is below 94% (some sources say 90%). Too much oxygen can be harmful — hyperoxia has been shown to cause direct vasoconstriction of the coronary arteries. If the patient is significantly short of breath or in CHF, some oxygen is reasonable, but keep it in the 94–99% range. No benefit has been found applying oxygen to a normoxic patient, and it could potentially harm them.

Morphine

Morphine was traditionally a mainstay for chest pain, but morphine given to heart-attack patients has been shown to potentially cause harm. NSTEMI patients treated with morphine were found to have an overall increased chance of dying — the leading theory is interference with the antiplatelet effect of agents like Plavix or Brilinta. Morphine can still be given, but should probably be limited to those with severe pain after other measures are in place.

3. The Bigger the IV, the Better

Nurses love to place large IV catheters, especially in the ED, and an 18-gauge is great for trauma or large-volume needs. But an 18g should not be your standard for every patient. Most fluids and medications run fine through 20g and even 22g. Defaulting to a 16 or 18g "because you can" has downsides:

Instead, place the size needed for the anticipated therapy. As a rule of thumb: 18g for suspected large fluid volumes (codes, hypotension, critical patients); 20g for boluses, maintenance fluids, IV pushes, CT angiography (in an AC line), or blood transfusion; 22g for boluses, maintenance fluids, IV pushes, or other IV medications. You can never go wrong with a 20g, and true emergencies benefit from an 18g.

4. A Nurse's Nose Knows C. diff

Clostridium difficile is a bacterial intestinal infection causing severe diarrhea, hospitalization, colon inflammation, and even death in older at-risk patients. If you've worked in the hospital, you've experienced it — and that putrid smell.

My first preceptor taught me that "C. diff has that smell." It often does — but are nurses' noses sensitive enough to tell C. diff from regular diarrhea? Earlier studies suggested yes, but in a blinded controlled laboratory setting, nurses could not tell the difference, performing no better than chance. Individual experience or confidence in detecting the smell made no difference.

5. If a Patient Leaves AMA, Insurance Won't Cover the Visit

As a new nurse I was taught that "if a patient leaves AMA, insurance may not cover their visit" — not to manipulate them, but to make sure they understood the financial consequences. What I didn't know is that this just isn't true. There's no basis for the claim: leaving AMA does not impact insurance coverage.

Over half of medical residents and nearly half of attendings have believed this myth too. We should absolutely explain the real consequences of leaving AMA — getting sicker or potentially dying from refusing treatment — but we should not mention insurance coverage, since it's untrue and can manipulate a patient into staying against their wishes.

6. High Fevers Cause Seizures

Many nurses, especially in the ED, have witnessed febrile seizures — common in children and associated with high fevers. But what if the high fever doesn't actually cause the seizure, at least not alone?

The true trigger seems to be a rapid rise in temperature, with high fevers lowering the seizure threshold. The higher the fever, the more likely a seizure, but the rapid rise is the trigger rather than the fever itself. Fevers also cause insensible water losses, dehydration, and hyponatremia, all of which lower the seizure threshold. Febrile seizures often accompany viral infections and can occur after certain vaccinations — the good news is they're brief and usually have no long-lasting effects.

And speaking of fevers — you don't always need to treat them. High fevers can be treated to ease symptoms and prevent dehydration, and treating fevers >102°F may help prevent febrile seizures in young children. But there's utility in not treating low-grade fevers, since fever is a natural defense mechanism the body uses to fight infection. If the patient stays hydrated, an antipyretic isn't always absolutely necessary.

7. Pseudoseizures Mean They're Faking It

Sometimes a patient has a "seizure" and we don't believe them — these get labeled pseudoseizures because they aren't true seizures. Not all seizures are the classic tonic-clonic Grand Mal, and sometimes people really do have "fake seizures." But does that mean they're faking it?

Maybe not. Those with a significant history of psychological disorders, trauma, and poor coping mechanisms can have psychogenic nonepileptic seizures. These are often psychosomatic, and the patient may not realize they aren't true seizures. Do some people actually fake it — for attention, or to get out of a DUI? Sure, it happens. But just because someone has a "fake seizure" doesn't mean it's fake for them. Try to maintain compassion and understanding, even when it seems like they're wasting your time.

8. Flu Shots Cause the Flu

This one seems basic, yet too many RNs perpetuate it. There is no possible way the flu shot can cause the flu. IM flu vaccines contain inactivated virus or a viral protein — neither can replicate or cause disease. It is physically impossible for them to cause influenza.

Common side effects after the injection — local reaction, body aches, low-grade fever, nausea, fatigue — are short-lived and probably represent your immune system creating antibodies. If you do get full-blown flu shortly after vaccination, there are several explanations:

A live-attenuated flu vaccine exists, but it's intranasal, not intramuscular. The flu vaccine is always recommended for healthcare providers, as influenza kills thousands in the US each year.

9. Vancomycin Is Broad-Spectrum

Vancomycin is a "heavy-hitter" we commonly give for MRSA, so it's commonly considered broad-spectrum. However, vancomycin is actually fairly narrow-spectrum. "Broad-spectrum" means a wide range of bacteria — gram-positive, gram-negative, aerobes, and/or anaerobes.

Vancomycin works wonders for gram-positive organisms (including MRSA), but has essentially no activity against gram-negatives — making it narrow-spectrum. That's why you'll usually see it ordered alongside another antibiotic. Why does it matter? In sepsis, antibiotics must be given STAT, and it's recommended to give the broad-spectrum antibiotic first. Vancomycin takes a while to infuse (1–2 hours), whereas a broad-spectrum agent like Zosyn or Cefepime infuses quickly (about 30 minutes) and should go first. See 6 Steps for Sepsis Management.

10. Toradol Works Better Than Ibuprofen

Toradol is an IV/IM NSAID we commonly give in the ED and inpatient — I tell patients "it's like IV ibuprofen." As an NSAID, it decreases inflammation, helps pain, and reduces fever, working well for migraines, kidney pain, and arthritic/orthopedic pain.

Since it's given IM or IV, most people assume it works better than a pill — reasonable, since many drugs work better given intravascularly with ~100% bioavailability and no first-pass effect. Interestingly though, studies do not show IV/IM Toradol is any more effective at reducing pain than PO ibuprofen. There also appears to be a ceiling dose for pain around 10 mg IV — meaning a 30 mg dose is no more effective than 15 mg.

11. Normal Saline Always Helps Hyponatremia

When sodium is low (<135 mEq/L), it's often due to dehydration, and Normal Saline usually improves it — dehydration is the most common cause of mild hyponatremia. But it's not always that simple; sodium is influenced by many factors. Simplified, treatment depends on fluid status:

Serum osmolality and urine electrolytes/osmolarity help, and a nephrologist can determine the cause and treatment. In general, with mild sodium decreases, elevated renal function, and a history of decreased PO intake or dehydration, you won't go wrong with a 500–1000 mL bolus followed by a slower maintenance rate while following labs.

12. Respiratory Rate Isn't Important

The respiratory rate is one of the vital signs, yet it's become commonplace to skip counting and simply chart "16–18". Why? Nurses and aides are busy, and counting seems like a waste of time — reinforced when the patient looks well with nothing respiratory going on.

As a new Med-Surg nurse I took over a patient at 11 pm. Something looked off — flushed face, breathing about 30 rpm — but she denied symptoms and her checked vitals were "fine." By morning she was found to be in severe metabolic acidosis secondary to renal failure, with a pH of 7.1. Her increased respiratory rate was respiratory compensation to breathe off CO2 — an important vital sign I should not have overlooked.

Be mindful to count accurate respiratory rates on anyone breathing fast or with a respiratory complaint. Best practice is a full minute since patterns are irregular, but any counting beats none — count for 10 seconds ×6, 15 seconds ×4, 20 seconds ×3, or 30 seconds ×2. The longer you count, the more accurate the rate.

13. Don't Let Concussions Sleep

After mild-to-moderate head trauma, many people develop concussions — a common ED presentation. There's a running myth that concussion patients shouldn't sleep because "they may never wake up." When my brother was hit in the head pitching in high school, I vividly remember trying to keep him awake in the backseat. (He did end up with a subdural hematoma — not the best example — but regardless, keeping someone awake won't really help them.)

The worry is that someone with a brain bleed who falls asleep will die unnoticed because no one recognizes their declining neuro status. While possible, this is unlikely from a concussion. What matters is that patients are evaluated, get a neurological exam, and possibly a head CT. Those who should get a head CT include:

If you're discharging a patient whose head CT showed no bleed, there's no indication for them to "stay awake" or be checked through the night — you've essentially ruled out a head bleed. Delayed bleeds can occur but are unlikely in low-risk concussion patients. If cleared, they should be encouraged to rest, which helps them heal. See The Cranial Nerve Assessment.

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