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Of all the abnormal urine colors, blue really stands out — both in terms of fright factor and rarity. What could be behind YOUR blue urine?

Blue Urine As The Side Effect Of Medications And Food Dyes

Blue urine is most frequently caused by methylene blue, a medication and a dye. Often used for diagnostic tests as a contrast agent, methylene blue is also a treatment for methemoglobinemia and refractory hypotension and sometimes cyanide poisoning and even urinary tract infections. In addition, the stuff is found in over the counter medications and home remedies in some countries, as it has some antibacterial properties. 

The medication, the first use of which dates back to 1876, comes with quite the list of nasty side effects except for the green or blue urine it can cause: nausea and vomiting, headache, confusion, hypertension, breathing difficulties, and the breakdown of red blood cells — among others!

Other medications that can cause blue urine include the antidepressant amitriptyline and propofol, a medication that helps you relax before receiving general anesthesia. 

Blue Urine Caused By Foods?

While pink and brown urine are quite commonly caused by foods, including beet and fava beans, blue urine is only really the result of two food items. If you have been eating asparagus or black licorice and your blue pee doesn't recur, you have almost certainly pinpointed the offenders. Artificial food dyes, however, may also have this effect. Blue sports drinks and blue-colored cakes come to mind.

Blue Urine Can Signify Medical Conditions

Rarely, blue urine is the result of urinary tract infections caused by the bacterium pseudomonas. If this is what you have, you will notice the burning feelings and frequent urination that go along with urinary tract infections, and notify your doctor in order to get some antibiotics prescribed to you. (If you don't want your blue pee problem to continue, you better hope you don't live somewhere where a doctor might prescribe methylene blue to treat your UTI!)

There's another medical condition, known so well for its ability to lead to blue pee that it's known as "blue diaper syndrome", however. The medical name for this condition is  familial benign hypercalcemia, and it is a rare hereditary disorder that is characterized by extremely high levels of calcium in the blood. 

Thankfully, familial benign hypercalcemia is, as the name suggests, benign. Though some patients experience fatigue, general weakness, constant thirst, and thought disturbances, many do not. Treatment is not usually deemed necessary, and the tell-tale blue urine is often what leads to the correct diagnosis. 

Blue Urine? You're Pretty Unusual!

Because the pigment urochrome, which normally gives urine its yellow color, will still be present, green urine is more common than truly blue urine. This is due to the simple reason that yellow and blue, when mixed together, tend to produce a green color. 

Familial benign hypercalcemia is the only condition that is specifically known to cause blue, rather than either blue or green, urine. Interestingly, linguistic research shows that people's ability to distinguish blue and green depends on the language(s) they speak to a great extent. As such, whether your urine is green or blue is perhaps not a matter of objectivity. 

Should you notice blue pee in the toilet bowl, it's always good to catch a sample in a cup, both to be able to take a closer look at it to make sure it really is blue, and to be able to present it to your healthcare provider — whom you should certainly pay a visit if your keep on passing blue urine. 

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