I can understand why you would be concerned given your location. Heartworm is indeed a problem in Texas.
So, you should re-start the Sentinel right away and re-test your dog in 6 months. Our blood tests will not pick up an infection that is less than 6 months old, so there is no point in testing any earlier than that.
If you re-start right away, odds are very much in her favour that she will be fine!
I hope that helps and allays your fears!
If it has, please hit the green "Accept" button and leave feedback.
I will still be here to provide more information if you need it – just click reply!
The above is given for information only. Although I am a licensed veterinarian, I cannot legally prescribe medicines or diagnose your pet's condition without performing a physical exam. If you have concerns about your pet I would strongly advise contacting your regular veterinarian.
Best wishes to you and to your dog!