The advantage of serum is that most insurance providers recognize this method and reimburse the cost of the test. The disadvantage is that what’s in the serum may not reflect what is in the tissue. Conceptually speaking, the serum represents the highway and the tissue represents the destination. It is thought by many that saliva and urine tests reveal the tissue levels. In our practice, we have tested both serum and saliva. Most of the time we will use serum to give us an idea of hormone balance or imbalance.