LetsGetChecked.ie or some other blood test, just to see if everything is ok?

So, I'm 33 and have been quite into fitness and eating well since the age of about 20. However, I've never actually taken a blood test or anything to see if I'm deficient in anything. I'd like to get a few things checked, testosterone levels, vitamin D, etc... I feel ok, but I'm noticing in the last year or two my mood hasn't been as great, I'm putting on fat easier and sex drive is lower. That could just be because I moved back to Ireland from a warmer country where I was outdoors a lot more, or it could just be normal aging, but I'd like to know for sure.

I don't plan on getting on TRT or anything, it's more just out of curiosity.

What would be the best way of getting checked. Using an at-home test like LetsGetChecked.ie? (They're a huge company but their Irish google reviews are pretty bad), or I saw there's also Bloodworks in Skerries. Anyone any experience getting tested?