For example, the clinic or hospital receives a subpoena demanding records of the defendant or victim in relation to the case however, the doctor isn’t at liberty on disclosing patient information as it contains their medical history alongside other sensitive content. Is it the same with companies not willing to disclose who their clients are even if they’re given a subpoena?
Not a lawyer, medical information in the US is more protected than most other types of information. For medical data specifically a subpoena is generally not enough, a judges order is more common and would likely be narrowed in scope as much as possible first. For other types of client privilege it can still be pushed back on/requested to narrow scope, etc. I should mention ignoring a subpoena in any case is NOT an option, you must reply to the court and go from there. Even if you just say “No” you have to say that, then let the court decide if they want to press the matter.