If you think your dog has eaten something that may have been fatty take them to the vet as soon as possible and ask for blood tests for pancreatitis. (caninejournal.com)
If your puppy is over 6 months, you can have simple blood test done at vet to check. (1800petmeds.com)
There are several simple blood tests for heartworm disease. (leandervetclinic.com)