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Transdermal patches (adhesive patches placed on the skin) may also be used to deliver a steady dose through the skin and into the bloodstream. Testosterone-containing creams and gels that are applied daily to the skin are also available, but absorption is inefficient (roughly 10%, varying between individuals) and these treatments tend to be more expensive. Individuals who are especially physically active and/or bathe often may not be good candidates, since the medication can be washed off and may take up to six hours to be fully absorbed. There is also the risk that an intimate partner or child may come in contact with the application site and inadvertently dose himself or herself; children and women are highly sensitive to testosterone and can suffer unintended masculinization and health effects, even from small doses. Injection is the most common method used by individuals administering AAS for non-medical purposes. 
Most testosterone hormone is transported through the blood via special carrier proteins known as albumin and sex hormone binding globulin (SHBG). When the carrier proteins with testosterone on board get to tissues that need testosterone, they will release testosterone so it can perform its functions. In addition to testosterone bound to carrier proteins, a small portion of the total testosterone hormone is known as bioavailable, or free, testosterone as it circulates unattached or loosely attached to the carrier proteins. This particular total testosterone test measures the total amount of testosterone attached to albumin and SHBG and bioavailable and reports it as one testosterone test result.