The vet did mention something about highish levels of albumin and calcium,
Depending on just how elevated the calcium level was, you may want to ask the vet about the need to run an ionized calcium level in the future to confirm it IF it is elevated again with repeat labs. Standard calcium levels can be effected by dehydration & given that the albumin level was also high (indicative of dehydration), it may have just been some dehydration effecting the calcium level (fingers crossed).
I have a cat who has been diagnosed with idiopathic hypercalcemia. Increased calcium can be caused by several serious underlying disease states (which could also be effecting his DM) so the process would be to get an ionized calcium level to confirm the finding & then the next step would be to get
X-rays and an ultrasound. Both are very important as a diagnosis of “idiopathic” hypercalcemia is what is called a diagnosis of exclusion.
All other diagnosis that are likely to result in an increase in calcium must be ruled out first before it would be deemed idiopathic. Even with a diagnosis of idiopathic hypercalcemia, quarterly repeat labs (including ionized calcium) & Bi annual ultrasounds are required to make sure additional problems aren’t developing.
So, it actually will be helpful on two fronts to get the diagnostic imaging (ultrasound) that is planned when the HST testing will be done:
1) Rule out any causes for an increased calcium/ionized calcium level (*if the ionized calcium is run & confirms hypercalcemia) Even if the ultrasound is done without an ionized calcium level & the calcium level is high on repeat labs & something is seen, they will be able to connect the dots

pretty easily!
2) Look for any organ enlargement potentially caused by HST/acromegaly *very important to know so it can be addressed (when possible)
I do not mean to overwhelm you with another possible issue

but it is best to have it on the radar

.
Oftentimes, when there is incomplete diagnostics & an attempt to bypass differential diagnosis, you run the risk of continued issues with DM management &/or with optimizing treatment, both short term and long term. It is always best, when possible, to be proactive, take your time and cross those t’s and dot those i’s, to try to prevent further DM management issues now.....and also later

.