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Definition - What does B Sample mean?

A B Sample is the second part of a split specimen taken from a biological specimen, usually urine, oral fluid, or blood, collected from a person who is being tested for drugs. The purpose of the B Sample is to prove the accuracy of the A Sample result. If the A Sample tests positive for drugs or tampering, the donor may request the B Sample be tested at a different laboratory if they disagree with the results of the A Sample testing.

SureHire explains B Sample

An employer may instruct an employee to be tested for the presence of drugs either as a pre-employment condition, as a result of reasonable suspicion, following a workplace accident, or as part of a random testing program. When an employee is tested for drugs, a biological sample (usually urine or oral fluid but athletic industry entities often require blood) is taken and split into two containers - one is marked as the A Sample while the other is marked as the B Sample and secured for possible confirmatory testing if needed.