Chocolate lab throwing up

Question
Good morning,
Our Chocolate lab has been throwing up randomly, more so when she is excited, full tummy or not. She is almost 13 years old, female and spayed. she just became a little grey in the chin in the last year. She does not eat people food and seems really young and spry most of the time. She has developed a little limp in her front right paw so in the past year and a half we have eliminated ball chasing  and just go for walks.

This morning she ate a lot of Grass and I noticed in her bile vomit there was a bit of blood. What does this mean and what can I do?

Answer
Dogs have never explained why they eat grass and throw up.  There is a lot of guess work passed off as fact.  It may be they know it will make them throw up when their stomach is bothering them.  It may be that they like grass and never learn, or don't mind throwing up.  

The bile is natural with an empty stomach.  The blood does bother me.  Perhaps at her age, you need to be a little quicker to see the vet.  It may be nothing, or an early symptom of something serious.