Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
Without the ability to examine you and obtain a history, I can not tell you what the exact cause of your laboratory abnormalities is. However I will try to provide you with some useful information.
There are many many causes to elevated CPK. Medications are probably the most common, with the cholesterol medications (called as a group "statins") being the most common. Besides medications, various muscle disorders, including autoimmune, inflammatory, genetic, infectious (viruses most commonly) and acquired disorders can also cause elevated CPK. An elevated CPK is most often a marker of muscle tissue breakdown. However, there is a condition called "idiopathic hyper-CKinemia" which is just an elevated CPK, without an identifiable cause, and with no clinical implications. However, the latter is a diagnosis of exclusion: other causes of elevated CPK must be ruled out. Have an EMG is on the right track for this.
LDH is an enzyme (a protein) found in many tissues in the body, including the muscles in addition to many others. There are many non-neurologic causes of LDH, but in general an elevated LDH indicates some sort of tissue damage, such as due to infection, blood breakdown (what is called hemolytic anemia), other blood disorders, and several others.
It sounds like you are on the right track with an EMG ordered, continued follow-up with an internist is recommenced. Evaluation by neuromuscular specialist (a neurologist specialized in muscle and nerve disorders) may be of benefit to you.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.
I have never heard of idiopathic hyper-CKinemia but that definitely seems interesting. If the EMG doesn't have any conclusive results then that might definitely be something I should talk to my neurologist about.
Thank you so much!