I recently had blood work done (non-fasting) for vitamin B1 deficiency. My levels came back as 6. Everywhere I have found it documented says that normal levels are from 8-30 in plasma, but my test says normal levels are from 4-10 and I don't think that is correct. Is my B1 low? I've been having persistent tingling for months now. I'm 22, female, healthy weight and balanced diet. I have paresthesia, fatigue, headaches and digestive upset, all with no explanation..