@Guwop2 - thiamine caused a refeeding syndrome reaction for me - the thiamine increased my need for phosphorous, causing a functional phosphorous deficiency. However, the B1 also gave me a nice boost in energy, so I wanted to keep taking it. But the energy boost was followed by severe fatigue (low phosphorous). It took a little sleuthing to figure this out.
Dairy products are high in phosphorous so I drank around 3 glasses of kefir and the horrible fatigue started to dissipate after a couple of hours. I eventually had to buy a phosphorous supplement which I continue to take, as well as the B1.
Methylfolate did something similar to me - nice boost in energy followed by severe fatigue, but that time it was caused by my potassium tanking. The methylfolate increased my need for potassium, causing a functional potassium deficiency. I started taking potassium gluconate (best form I could tolerate), titrated up to 1000 mg a day (in divided doses) and the fatigue went away. I still take the methylfolate and potassium and do well on it.
Muscle testing has helped me a lot with these issues and several others, though I recommend having it done by a competent practitioner (very often a chiropractor) before attempting it oneself.