Disclosed is a method of treating in a subject hair loss disorders that are beneficially treated by administering a JAK1 and/or JAK2 inhibitor. The method comprises administering to the subject an amount in the range of about 4 mg to about 50 mg of Compound (I):




or a pharmaceutically acceptable salt thereof. This invention also provides compositions comprising Compound (I) and the use of such compositions in the described methods.