If you want to know how labs determine certain levels of a vitamin or mineral in blood, you would have to research the chemical makeup of the blood panels they use and the mechanics behind certain machines/how they work in being able to identify whatever it is that's being tested, including the quantities. I also tried researching this and found it extremely difficult. All I can assume is that the chemical makeup of the tests interacts with the blood components in a way that allows the medical lab technician to approximate the levels of whatever substance they were looking for. I'm sure you can buy these panels yourself, however several problems will arise if you do so:

1.) Blood panels can be VERY expensive, depending on what you want to test for.

2.) If you don't know how to prepare the blood (which I'm assuming you don't as you're not trained to) in a way that's necessary for the test to work, you're wasting your time and money.

3.) Most blood tests require centrifuges and/or specific machines.

4.) Reading the results of blood tests requires the expertise of a licensed lab technician.

Doctors usually do not carry out tests on blood. They may get involved if the test results come back as abnormal. Tests are performed in labs by biomedical scientists. Most tests nowadays are done on machines generically referred to as analysers. They test the blood and produce results. There are even machines which can now prepare blood and bone marrow smears on slides and read them. If results of tests come up as abnormal the lab's biomedical scientists may do a number of things. They may repeat the test. They may do an alternative test. They may manually perform the test or an alternative. If results are still coming back as abnormal they will be referred to a doctor called a haematologist. They may then carry out further investigations.

Doctors don't usually perform the blood tests. MLTs/CLS's do this in labs. They now do it with automated machines either in house or send out to some lab which turn over results in 24 hours time. Something called a comprehensive metabolic panel can be performed.

A centrifuge is the one of the least difficult or ridiculous of the equipment. Blood needs to be separated into different components to test it more easily for certain substances...

With then progression of CLIA waved self tests, you may be able to purchase specialized kits for what you are testing for exactly. These kits tell you what to do.

Google or yahoo "CLIA waved test list" for a long list of tests you could perform at home with the correct kits. They are not error proof.

I don't think there is an all in one kit because if there were, then why would people even go to the doctor or get blood tests? Then doctors and labs would run out of money and job loss would be terrible.

When I looked through the list, I did not see vitamin D test, yet amazon claims they have a kit... so be careful.

With your microscope, if you view the cells at 400x, you would be able to see what your cells look like if you do a blood smear properly, and if there is a kit that allows you to place the cells in quadrants, you could do a crude blood cell count with differential. You could also see if cells are the right size and shape. This is just one possibility, but a microscope would not be able to detect deficiency of vitamin D.