Why is my dog in heat sick and not eating after being outside?

These are not normal symptoms associated with being in heat, so I would be concerned about some other illness. If she hasn't eaten in several days and is still vomiting, I would recommend taking her to the emergency vet. She is likely very dehydrated at this point, and we need to figure out what is causing the nausea.

Dogs have heat cycles and not menstrual cycles, however it is possible she is going into heat and hence the behavioral change, though she shouldn't refuse to eat, or be extremely lethargic during. If it persists for more than a day, doesn't improve, or her symptoms worsen, it is best to seek out veterinary care to rule out issues such as an infection or another illness that could be causing these symptoms as well.

Poor girl. Some dogs have a tougher time than others when it comes to their first heat cycle. However she does seem to bra late bloomer as most dogs have their first heat cycle around 6-10 months. If she is this ill I would recommend having her to examined by your vet to make sure she isn't having any complications or other underlying illness that's causing this. If she is found to have a ln abnormally intense heat cycle, then the vet can prescribe some safe pet friendly pain medicaiton for her to get for the next few days until the brunt of her menstrual cycle has passed. In the meantime I try placing a warm compress on her belly for a few minutes (be very careful not to leave on too long or you can easily burn your pets skin) to help ease some of the discomfort. hope she feels better soon!

Dogs can feel lethargic and not want to eat during their heat cycle especially their first one. However, this shouldn't last long. Vomiting is a bit unusual for a heat cycle. She should get a physical examination by a veterinarian to make sure she doesn't have gastroenteritis or pancreatitis.

I can certainly understand being concerned about Tulip! Lethargy is a very general sign of illness, and it can be caused by systemic illness, infection, inflammation, or injury. I would keep an eye on her tonight, and if she is still acting this way in the morning I would take her into a vet first thing for a health check.

Being in heat can cause behavioural changes in dogs, as long as they are not too extreme and the dog is otherwise well I would not worry too much. Quite often when in heat dogs well be lethargic and not want to eat very much.

Vomiting is not usually a symptom of being in heat. It sounds as if she might have eaten something that either disagreed with her or something that has gotten stuck somewhere in her gastrointestinal tract. She could have been exposed to some sort of toxin or irritant in her environment or this could be early signs of another condition or disease process. She could also have a uterine infection causing these symptoms. I recommend getting her seen by your veterinarian as soon as possible. Your vet will do an exam, blood work and possibly x-rays to determine the cause of the illness and suggest an effective treatment plan. Additionally, unless she is a purebred that will improve the breed by producing offspring, I highly recommend getting her spayed once she is over her illness. This will eliminate the chance of her getting a life-threatening uterine infection and greatly reduce her chances of developing breast cancer in the future.