S.C. Code Ann. § 56-1-2130

(A) A person who drives a commercial motor vehicle within this State is considered to have given consent, subject to provisions of Section 56-5-2950, to take a test of that person's blood, breath, or urine for the purpose of determining that person's alcohol concentration or the presence of other drugs. (B) Tests may be administered at the direction of a law enforcement officer, who after stopping or detaining the driver of a commercial motor vehicle, has probable cause to believe that the driver was driving a commercial motor vehicle while having a measurable amount of alcohol in his system. (C) A person requested to submit to a test as provided in subsection (A) must be warned by the law enforcement officer requesting the test, that a refusal to submit to the test must result in that person being placed out of service immediately for twenty-four hours and being disqualified from operating a commercial motor vehicle for not less than one year under Section 56-1-2110. (D) If the person refuses testing, or submits to a test which discloses an alcohol concentration of four one-hundredths of one percent or more, the law enforcement officer shall submit a report to the Department of Motor Vehicles certifying that the test was requested pursuant to subsection (A) and that the person refused to submit to testing, or submitted to a test which disclosed an alcohol concentration of four one-hundredths of one percent or more. (E) Upon receipt of the report of a law enforcement officer submitted under subsection (D), the department shall disqualify the driver from driving a commercial motor vehicle under Section 56-1-2110.