It depends on whether your symptoms correspond to what happens when your levels of these. things are out of balance. I assume you had a Tsh test for your thyroid, but know that it doesn't actually test your thyroid -- it hints at potential problems but the only way to tell for sure is to test your free T3 and T4, the hormones considered most significant in the thyroid. These days many docs do recommend D supplementation because people just don't go out in the sun anymore, and it's true that being the in the lower range of thyroid or B12 does affect some people negatively. Again, though, you don't state what's going on, just that you generically don't feel good, and you probably told your doctor more than what you're saying here and your doctor isn't concerned. But doctors are fallible. It's pretty easy to do a test of B12 by taking a sublingual supplement of the methylcobalamine form, but if you take too much for too long it is possible to throw your B6 and folate out of balance as the three are in balance together. But with so many nutrients out there to choose from and so many things in your diet or lifestyle or genetics that can go wrong, why did you choose to focus on these three particular items? What's going on?