I had to look it up, and this is what I found
Creatine kinase (CK) is an enzyme that mainly exists in your heart and skeletal muscle, with small amounts in your brain. Muscle damage causes increased CK levels.
my.clevelandclinic.org
You are doing a keto diet abd one side effect can be that as you drop the carbs but do not compensate the loss of glucose energy by increasing either protein or fat, then the body makes its own energy by scavenging muscle tissue and converting it to glucose.
Perhaps a google of Professor Tim Noakes would help explain better than I can. He is one of the keto diet grand masters who is also a fitness coach and athlete.
Working out on keto may be stressing your muscles and raising the creatine. It sounds counter productive to increase fat but that is what LCHF is all about. The HF in my mind stands for Healthy Fat, but it is usually referred to as higher fat.