My urine culture is negative, can I still have a bladder infection?

In a word, yes.

And this is a difficult concept for many doctors to get because we have long been taught that the gold standard is culture.

Let’s back up a little. These are the symptoms of a bladder infection:

• needing to empty your bladder a lot (urinary frequency)
• when you gotta go, you gotta go (urgency)
• pain just over the pubic bone
• blood in the urine
• burning when you empty your bladder, some women say it’s like peeing razor blades (dysuria)

If you have any one of these symptoms of a bladder infection there is a 50% chance you have one. If you have both burning when you pee (dysuria) and need to go a lot (frequency) and don’t have vaginal discharge or vaginal irritation there is a 90% chance you have a bladder infection.

So with this information in mind, if your symptoms are classic there’s a pretty good chance you have a bladder infection and you may get treated over the phone without a culture. However, if your symptoms aren’t classic or you have been suffering from recurrent infections your doctor should do a culture, meaning have the lab try to grow bacteria from your urine. Another advantages to growing the bacteria are to confirm you are on the right antibiotic.

So what if the urine culture is negative, but you or your doctor are convinced your symptoms are a bladder infection?

Bacteria colonies (not from a lab, this is from my kids’ science fair project, but you get the picture)

Urine cultures report the amount of bacteria in the urine, and usually only report 100,000 colonies (groups) of bacteria per ml of urine (see this clip if you want to see how it’s actually done) or more. Many labs report 10,000 colonies of bacteria/ml of urine or less as negative although some use 50,000 colonies/ml as their negative cut off. The problem? At least 30% of adult women with a bladder infection will have 10,000 or fewer colonies/ml.

So….what’s a girl who thinks she has a bladder infection to do?

If your symptoms are not so classic, most doctor’s will get a microscopy test (look at the urine under the microscope) while waiting for the culture. The microscopy test is about 87% accurate, meaning it will still miss some infections.

But there may be a situation where your or your doctor are pretty convinced you have a bladder infection (either based on your symptoms or the microscopy) and then the urine culture is read out at negative. On the assumption that you could be one of those women who gets an infection with 10,000 or fewer colonies of bacteria per urine it may very well be worth treating you for a bladder infection to see if you improve. Follow-up is essential because you should be feeling almost 100% within 48 hours, so if you are not then something else may be going on.

In an adult woman a negative urine culture does not necessarily rule out a bladder infection.

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Remember, this post does not represent direct medical advice