You go to the emergency room with “down there” symptoms: You need to pee more often than usual and it burns when you do. You also may have pain in your lower pelvis.

The ER doc takes a urine sample. When it comes back abnormal, he diagnoses you with a urinary tract infection (UTI). You head home with a prescription for antibiotics, relieved to know what’s wrong and that you’ll feel better soon.

Not so fast.

A new study finds that emergency room doctors frequently misdiagnose urinary tract infections, as well as sexually transmitted infections (STIs). And sometimes they mistake STIs for UTIs. After examining the records and urine samples of more than 260 women ages 18 to 65 who visited MetroHealth Medical Center emergency department in Cleveland, scientists from Case Western Reserve University found that fewer than half of those diagnosed with a UTI actually had one. At least 37 women had STIs that were missed entirely. (The STIs tested for were chlamydia, gonorrhea and trichomoniasis.) 

“Our research found that UTIs are often over-diagnosed and STIs are often under-diagnosed in emergency settings,” says study author Michelle Hecker, MD, an assistant professor at Case Western Reserve University’s School of Medicine.

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Why the mix-up?

Urinary tract infections and STIs have similar symptoms. Both can produce an abnormal urinalysis result as well.

“Emergency room providers appear to rely heavily on urine tests since they come back quickly,” adds Hecker. “But just having an abnormal urinalysis or even a positive urine culture does not mean you have a UTI that needs treatment.” Although her study focused on ER diagnoses, Hecker believes it’s likely that women and even non-ER docs also may muddle the two conditions.

The biggest problem with this error? Taking antibiotics unnecessarily for a non-existent UTI. “Antibiotics can be life-saving,” Hecker says. “However, if not used appropriately, they can have significant consequences.” The biggest risk is antibiotic resistance, which can affect personal health as well as public health. 

Antibiotics also can have ugly side effects, including allergic reactions, diarrhea and bad interactions with other meds. According the Centers for Disease Control, 50 percent of the time antibiotics are prescribed incorrectly.

Related: 5 Common Antibiotic Mistakes

What’s more, you won’t get the treatment you really need. That means if you have a sexually transmitted infection such as chlamydia or gonorrhea but are treated for a urinary tract infection, your STI is likely to rage on, get worse and potentially spread. Some 20 million new STIs occur every year, according to the Centers for Disease Control and Prevention, and while many go unreported, many more are undiagnosed.

Getting it right

You don’t need a medical degree to protect yourself from a misdiagnosed UTI or STI. Let Hecker’s guidelines empower you.

Become symptom savvy

Learn the similarities of and differences between a urinary tract infection and a sexually transmitted infection.

  • Symptoms that UTIs and STIs share: frequent urge to urinate, burning with urination and lower pelvic pain
  • Symptoms that suggest an STI: vaginal symptoms such as discharge, bleeding and/or irregular periods, and being sexually active and/or having more than one sexual partner in the last year (Just to make it more complicated, being sexually active also puts you at higher risk for a UTI, according to the Mayo Clinic.)

Speak up and be tested

  • If you’re diagnosed with a UTI based on an abnormal urinalysis or a positive urine culture but you don’t have lower urinary symptoms, definitely question the diagnosis. In Hecker’s study, 24 percent of women diagnosed with a UTI had no UTI-related symptoms
  • If you’re diagnosed with a UTI but you have vaginal symptoms (discharge, bleeding or irregular periods), and you’re sexually active, ask to be tested for genital tract infections (STI and other)
  • If you’re diagnosed with a UTI and have only lower urinary symptoms, you still may benefit from more definitive testing, including urine cultures and specific STI testing, Hecker says. Talk to your doctor about your specific symptoms and your risk factors for these infections.

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