I believe blood analysis is a viable tool that does give one an insight into ones health at a cellular level.
Years ago I was very ill and couldn't get help from mainstream medicine. The standard blood test showed I had chronic eosinophilia, slightly elevated blood sugar, slightly elevated bilirubin, but the doctors couldn't give me any diagnosis, even though there was obviously something wrong.
So I went to an alternative health clinic and had a live blood analysis. It showed I had an excess of fat in my blood, excess yeast, bacteria, malformed blood cells, and that I was infested with Babiesia. I sat next to the woman and saw little black parasites on the inside of my blood cells( with my own eyes)!
Then my girlfriend had hers done right after, she had a little yeast in her blood but other than that her cells look healthy and was free of parasites.
I went to the doctors telling them about what I saw, and they dismissed what I had to say, because all their test had come back negative. After three years of having weird labs without a proper diagnosis My conclusion was that most of the medical test they performed on me are bunk and were a worthless waste of time.
After the blood analysis I began to add everything together. The high Eosinophil count, liver congestion, spleen pain, fatigue, and all my other symptoms pointed to the fact that I had blood parasites, yet the medical establishment refuses to acknowledge the majority of these kinds of cases. They never took into consideration that I had a damaged spleen from a prolonged bought with Mono and so my body was incapable of properly filtering out parasites that most people could deal with easily.
I can testify that these parasites exist and can be detected in blood analysis, though I am still skeptical about the standard recommendations of many alternative health partitioners regarding parasite cleanses and flushes. They were not effective for me, and I only started to get better after I eliminated the foods that I had bad reactions too, and began to nourish myself back to health a raw paleo diet.