Get Your Dog Care Questions Answered by Experts
Hello and thank you for using this site to help you. I am sorry no one was able to get to your question sooner. When it comes to a dog being more quiet or depressed it is usually a sign of an illness, could be short lived or it could be something like Lyme disease or in a Lab at this age I would want a thyroid test done as a thyroid problem will show intolerance for exercise. The thyroid only has to be out of sequence a little to cause a problem. Blood tests might be in order to get to the root of the problem depending on how long it has been going on, especially if there is no change in eating, drinking, or eliminating,
To be on the safe side I would take her vital signs at home to determine if there is any emergency that need immediate care.
The gum color and capillary refill time will show an emergency as will a fever. A slow heart rate may also cause tiredness, depression or lethargy.
This link will take you through how to take the vital signs so you can decide if you need emergency care.