I took xanax before my bloodwork and tested with a high cortisol level. Doesn't xanax reduce cortisol levels?

No. HPA axis abn. Must do w/u for Cushing's disease vs syndrome via endocrinologist. Anxiety stemming from endogenous depression also keeps cortisol high. A DST or dexamethasone suppression test, can help to distinguish it all. If not Cushing's, then, antidepressants likely to normalize high levels, avoiding tolerance by Xanax.