Cat related

Tonight, was and is one of the most depressing nights. My fiance and I double dosed insulin to our 5 year old cat. I had given it to our cat and mistakenly didn't write it down. I verbally told her that I administered it. I went for a walk with the dog not knowing if she heard me or not. Long story short, she didn't hear me. What should I do in this situation with our cat being double dosed?