And For My Next Trick – Urine That Glows In The Dark!

And For My Next Trick – Urine That Glows In The Dark!

This is one of my favorite toxicology tricks and tidbits – I’ve actually witnessed this several times over the years. Drink some antifreeze and your urine may glow a weird blue-green color.


Ethylene glycol, the chemical alcohol in antifreeze, is one of the most lethal poisons in the world. It’s an incredibly effective way to kill someone, as we have documented here over the years. Antifreeze is easily available, it has a sweet taste and can be hidden in other drinks. A few years ago, a doctor in Texas poisoned her lover (another doctor) by adding antifreeze (ethylene glycol) to his coffee. He thought it was a little strange, since he didn’t normally add sugar or sweetener to his coffee, but his girlfriend insisted that he drink it. Later in the day, his kidneys failed. He lived but with permanent kidney damage. 

The ethylene glycol is metabolized via alcohol dehydrogenase and aldehyde dehydrogenase to form about 6 different organic acids. The body uses all its bicarbonate stores to neutralize the acids and the kidneys pay the price. The glowing urine isn’t particularly dangerous – its just a marker of fluorescein exposure. Fluorescein is usually added to antifreeze so mechanics can spot leaks when they examine your car with a black light. Fluorescein in the urine will make the urine take on a glowing blue-green when it is examined under a black light. 

The color change is not always that obvious. It can sometimes be very subtle and the plastic container that the urine is in can sometimes appear to glow under the black light. This color change test SHOULD NOT be used to either rule in or rule out ethylene glycol ingestion. It simply isn’t sensitive or specific enough. Certainly if you shine a black light on a patient’s urine and it glows blue-green, you need to work up the patient, get an ethylene glycol level and consider providing the patient with a dose of fomepizole (Antizole) until your lab tests come back (may take 24 hours or more in some areas of the country). 


Ethylene glycol (antifreeze) is one poison that doctors CANNOT afford to miss. Even very small doses of this poison can kill. Its unfortunately used often to poison household pets and garden pests. 

Written by Poison Boy

Gerry O'Malley (a.k.a Poison Boy) is a board certified ER doctor and toxicologist with a interest in the unusual, terrifying and occasionally hilarious world of poisonings and toxicology. This site is an exploration of poisons of historical interest as well as in current events and pop culture.

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