Knowing biology, I'm sure it's complicated and any generalization will be false. For example, there might be genetic conditions that derive from having two X chromosomes that we could argue are intrinsic to the sex (or more accurately, intrinsic to that karyotype), but for the most part my understanding is that differences relevant to lab ranges are mostly mediated by hormones, so I use female ranges.

Either way, my PCP seemed to indicate I shouldn't disclose trans status but that the one exception was that I eventually need to find someone for prostate exams once I hit that age (if I hit that age, I guess). The endo that prescribes my HRT has never mentioned whether I should disclose or when to.

I should say, even when my medical chart was shared across hospital systems and my gender dysphoria was listed in my chart, the ER doctors didn't seem to do uptake or change the way they treated me, even when I walked through my HRT and explained I couldn't be pregnant. They still thought I was a cis woman and asked if I could be pregnant - I think people mostly just operate based on what they see, and it's a shock when you say you are trans. It creates an extreme chilling effect sometimes, people stop meeting your eyes, or even interacting (sometimes interacting through a third party instead, like a cis family member). I've even talked to a neurologist through the details of my vaginoplasty and he didn't seem to do uptake that I was trans. Unless I say the words, they just won't put the dots together. (Meanwhile a trans woman at Sephora's will clock me from across the store.)

A good chunk of lab values have different ranges for male vs female.

You've actually hit on a major reason why disclosing isn't as simple as you think it is.

Sure, a good chunk of values have different ranges for male vs female, but the normal ranges for cis folk and trans folk are not the same.

Hormones are the obvious example, but there are large parts of the body that respond to the endocrine profile that we have after hormone replacement. Heart attack symptoms, body fat percentages, resting heart rate, blood oxygen levels, iron levels etc, are all shaped by our hormone profile, not the hormone profiles of cis folk.

That said, I have no idea if those are intrinsic to the sex, or to the hormone levels, so HRT might completely negate or flip those differences.

It entirely depends on the specific medical issue, but in general, it's the latter more often than the former.

I'd run this by your HRT doc.

It's not always that simple. On top of the fact that it's not realistic to see the HRT doc every time you have an unrelated medical issue, the other aspect is, as you're probably aware, sometimes, the patient knows more about their health care needs than the treating doctor, because we need to become experts in a way that a GP does not. If your doctor isn't a specialist in trans care, they're just as likely to give you conservative, incorrect information that was drafted in a time when trans health care even less understood than it is now.

As you're a nursing student, I want to give you some advice. When you are dealing with a patient that isn't "new" to their situation, whether it's trans health care, or long term illness etc, you need to allow for the fact that the patient likely has a lot of lived expertise in dealing with their situation, and broad, general advice is rarely going to be useful to them.