Order metabolic panel (chemistry/SMAC) blood testing online
In the majority of US states you can order metabolic panel testing online and have the blood drawn at a local blood draw center (see my general overview of the process).
I'd suggest ordering from Walk-In Lab because they have the cheapest price I know of ($28), and I've been happy with their service. You can also compare the other 4 metabolic panel test providers I've found.
Sources for a slightly-cheaper "basic metabolic panel"
A basic metabolic / chem panel (BMP8) leaves out the protein and liver tests from a comprehensive panel. The price difference is small enough that I always get the comprehensive, but if you'd like to compare, here are the basic panel providers I found:
I've been working to understand these levels better (I've always been on the low end of the references ranges no matter what crazy diet / supplement routine I've been doing, so I've been compiling some resources on it:
This document was useful for me in understanding the relationship between different markers, and for the explanation, "the serum (venous) value that is measured in the chemistry lab is the total CO2, it represents the bicarbonate moiety (HCO3) that is buffered by organic acids."
Mike Lustgarten discusses the levels he thinks are optimal (higher being better) for longevity. He does the same for the "anion gap".
Mike also discusses influencing the levels with diet, including information on calculating a diet's PRAL and NEAP values for estimating its effects.