Friends dog ate 2 mice might have been poisoned?

hey, just wanted to ask a quick question, my friend told me her dog ate 2 mice and that shes wondering if they were poisoned (prob eaten rat poison) and her dog has begun shaking, it ate the mice yesterday and now shes apparently woken up to the dog shaking, is this a symptom of poisoning? and what to do if it is? is it lethal?