Candidates for certification typically need some classroom education, as well as some clinical experience. Certification testing usually includes a written exam and may include practical components, such as drawing blood. Requirements vary by certifying organization. California, Louisiana, Nevada, and Washington require their phlebotomists to be certified.
Bureau of Labor Statistics, U.S. Department of Labor, Occupational Outlook Handbook, Phlebotomists, on the Internet at https://www.bls.gov/ooh/healthcare/phlebotomists.htm
NPA requires a minimum of 200 hours of theory and clinical in order to qualify to sit for the NPA exam. This can take a few months depending on your school program.