My Mom has a dog named Shaffer who weighs about 80 lbs. I stopped by to give him his heart worm tab because I always give it to mine on the 5th. When I went to her calander to put on the sticker, She still had up last month. I registered shock because she had written down on the 26th of October heart pill. She says she didn't give him anything. But if anyone wrote it down, it had to be her. SHe is 88 and gets confused which is why I wanted to be the one to dispense the pill. So that was 10 days ago. He takes Heart guard chewable tablet. I looked on line about over dose and this was all I saw. Quote from one site What are the possible side effects of Heartgard Plus: Side effects of Heartgard Plus are rare at the recommended heartworm prevention dose. Higher doses in dogs may cause tremors, dilated pupils, and loss of body weight and death. I don't even know if she gave it, if she wrote it on the wrong date, I don't know what to do. Is that enough time for a dog his size to not have adverse reactions? I am worried.