A blood test tells me my cholesterol level. any similar thing to know how strong my immune system is, approximately speaking?

It's complicated...: Your overall health and lack of frequent infections is the easiest gauge of the strength of your immune system. Usually this system is nearly perfect--it has to "win" every "battle" it fights, and does. It bats 100%. If you are having too many infections, yes, we can do tests to find out about your immune system, but they are numerous, involved, expensive and rudimentary vs what we will have soon.

Cbc: I would have you pcp check your complete blood count.

Blood counts help: The white blood cell count is divided into several subgroups that tell us different things. The neutrophils tell us how well you can make pus and kill invaders nonspecifically and the lymphocyte count tells us how the brains of the immune system are doing, roughly. One easy test we start with is an expansion of the lymphocyte count, called a lymphocyte subset test.