Can carpal tunnel cause complete loss of hand function?

If the nerve problem is severe enough, you can lose some hand function. It is unclear what you mean by complete loss. If the carpal tunnel syndrome is corrected, you will likely re-gain function. You may need some hand therapy. Good luck to you!

Since three major nerves innervate the hand muscles and sensory functions, a complete loss of median nerve function would not cause a "complete loss". If the sole pathology is carpal tunnel syndrome, there would be pain, numbness, and grip weakness, again not a total disability of hand function.