A thyroid panel and a standard blood count do not diagnose autoimmune gastritis, an immune attack on the acid-producing cells of the stomach. It is about five times more common in people with autoimmune thyroid disease. That includes both Hashimoto's and Graves' disease. It often surfaces as iron deficiency that does not correct, with B12 deficiency following later.

Bartonella is a bacterial infection that often appears alongside Lyme. In the US there is no current evidence that ticks transmit it, and the question is still under investigation. The proven routes are cat scratches and bites, cat-flea feces, and body lice. It is hard to detect, which is why a thorough Lyme workup checks for it properly.

Babesia is a malaria-like parasite carried by the same tick that carries Lyme. Because it is a parasite and not a bacterium, the antibiotics typically used for Lyme have no effect on it. It is seldom tested for, so people can finish Lyme treatment, still feel sick, and not understand why.