Functional medicine aims at understanding the root causes of illnesses when possible. There are hundreds of functional medicine labs available. Below is a list of labs I use the most in the beginning.
Micronutrient Testing (Spectra Cell) provides a comprehensive nutritional analysis. This approach provides a snap shot of nutritional state in the body. The results provide for deciding daily nutritional supplements.
Alpha Lipoic Acid
Spectrox® Total Antioxidant Function Immunidex Immune Response Score
2. DUTCH COMPLETE (Precision Analytical)
The Dutch Complete™ provides a comprehensive assessment of sex and adrenal hormones and their metabolites. It also includes the daily, free cortisol pattern, organic acids, melatonin (6-OHMS), and 8-OHdG. I use this test as a starting point for assessing adrenal hormone patterns (for cause of fatigue), sex hormone status, and rudimentary organic acid analysis which serve as metabolic markers for various functions such as B12, B6, Biotin, Glutathione, Dysbiosis, Neurotransmitter, Neuroinflamation, Melatonin, and Oxidative Stress. The major difference between Micronutrient Analysis and organic acids is that the former offers direct measurement while the latter offers metabolic inferences.
3. Food Allergy/Sensitivity Test
There are many companies utilizing different technologies to assess food allergy and food sensitivity. I favor a test that at least provides IgE and IgG anti-body response. P88 Dietary Antigen Test (Precision Point Diagnostics) provides IgE, IgG, IgG4 and complement (C3d) reactions to 88 of the most common foods found in the diet.
This topic is fully explored in below article - https://www.functionalnutritionanswers.com/what-is-the-best-food-sensitivity-test/