Thyroid peroxidase antibody (TPOAb) test: Less than 9 IU/mL. Thyroid-stimulating immunoglobulin (TSI) test: Less than 1.75 IU/L. Thyroglobulin antibody (TgAb) test: Less than 4 IU/m. Click here to get full list of functional medicine ranges for other thyroid blood markers. They are much narrower than standard ranges used by GP and they will help you to explain why you are feeling certain way even though your results are "within the range" according to standard reference ranges.