Thank you for your patience. Daisy's symptoms are certainly very concerning and if she has been off food for 3 days now, and has become quite weak as a result, then this is very serious indeed. We need to consider a wide range of possible causes for your girl's symptoms here including anything from an infectious cause, to a toxicity (hopefully there isn't anything around your home or yard she could have gotten in to), to an internal organ issue, or potentially even a blood disorder/anemia given her symptoms. The combination of her vomiting and then having these symptoms (at such a young age), do make me worry most about a potential toxicity or poisoning.
The sooner you can get Daisy to your local vet for a full check over and blood tests, the better. If she is particularly lethargic now, then I would recommend that you get her seen by your local ER vet right away if that is possible. If you can't get her seen right now, then definitely follow up with your local vet first thing tomorrow for a full physical exam and diagnostics to work out what is causing these worrying symptoms. For now, please keep an eye on her mucus membranes, capillary refill time and respiratory rate tonight as follows (do be careful that your girl doesn't try to bite you):
Mucus membranes - flip her lip and look at the color of her gums. They should maintain a nice salmon pink color. Get her to the emergency Vet if they appear white or very pale pink, or if they are a dark deep red color.
Capillary Refill time - this measures blood perfusion and test this by putting your thumb on her gum to apply pressure. After you release your thumb you will see the gum blanch. Capillary refill time is the amount of time it takes (in seconds) for the gum to return to a healthy pink color from the blanched white color. If 2 seconds or less don't worry - if it is taking significantly more time, again - off to the emergency Vet.
Respiratory Rate - if she seems to be panting or breathing rapidly throughout the night, this is a sign of shock and or pain and a signal for a trip to the emergency Vet.
If Daisy still seems quite nauseous, or if she has had the odd vomit since Wednesday, then you may also want to try her with a little pepcid. The typical dose for this type of situation is 0.25mg per pound of body weight up to twice daily. You can read more about the use of Pepcid in dogs online here: http://www.petplace.com/article/drug-library/library/over-the-counter/famotidine-pepcid
Best of luck with Daisy, and as above - these symptoms are very serious. Please do what you can to get her seen first thing tomorrow morning, if you can't get her seen now. I hope all of the above makes sense? If you have more questions or if I can help in any other way, please do not hesitate to ask! If you would like to accept my answer, please press RATE OUR CONVERSATION (I am not compensated in any other way). Bonuses are always welcome. Thanks! I hope to work with you again soon!
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