Dog with metallic breath

I have a year and a half old miniature doxie.  She is over weight and on a special diet.  She seems very happy with the food and has been using it for about a month and a half and has lost a fair amount of weight.  Lately though, within the last week or so, she has developed bad breath, but it is odd.  It smells metallic to me.  She doesn't act strangely, she eats normally and drinks water about the same as before.    We give her a "greenies" dog treat every two or three days and they are supposed to freshen breath.  She is mostly an inside dog but does play outside in our fenced yard.  We can find nothing she may have gotten into either around the house or the yard.  Is the metallic breath a known symptom of anything?

[Aleda M Cheng, D.V.M., C.V.A]

It could be from dental disease, which would be unusual for a young dog, unless she has retained deciduous canine teeth (baby teeth that never fell out), and there is a bit of blood around the base of these teeth.  A traumatic injury to the mouth that has caused some bleeding could cause this also.  

Bad breath can also come from further down in the digestive system: the stomach, intestines. etc.  If there is no problem with her mouth try giving your dog some probiotics in the form of Activia yogurt, and  over the counter digestive enzymes, such as papaya enzyme.