How is Urea Formed and Excreted?

One of my students asked me recently if ammonia was a breakdown product of bile. 

​I was very confused. 

Then I realized that she had been listening to a lecture on the various roles of the liver and had gotten a few things mixed up.

​What she really meant was, "What's going on with ammonia, how is it related to the liver, and why is it a bad thing?" 

Here's my answer:​

Voilà. Hope that helps to clear things up and answer the question, "How is urea formed?". 

One thing I didn't mention in the video is that a very small amount of ammonia (actually ammonium) travels in the blood under normal conditions. ​

That's it for now. Let me know if you've got any questions.

- Camille​


  • ​Fun quiz to test yourself on excretion & the liver from Chemistry for Biologists: click here
  • When ammonia becomes toxic article.
  • Here's the letter referenced in the previous article. 
  • Learn more about urea cycle disorders/disease
  • More detail about the urea cycle from the biochem perspective
Thanks for sharing!
Camille Freeman

Hi there. I'm the hippie who started Physiology for Hippies. I'm an associate professor at MUIH, where I teach physiology to students in the herbal medicine, nutrition and yoga therapy programs. I have two small children, an overgrown garden + an endless appreciation for the human body.