Acanthosis Nigricans is skin disease that associated with hyperinsulinemia. Clinical is velvety hyperpigmented plaques on neck, axilla, groin. If hyperinsulinemia is improved by treated with oral metformin and/ or diet control, acanthosis nigricans would be improved as well. Hyperpigmented plaques will be changed. We assess objective measurement by using spectroscopic and colorimetric analysis.