testing prior to starting hormonal therapy

what routine baseline labs should one have prior to starting tamoxifen (for preventing recurrence of Breast cancer)?
Is the tamoxifen metabolizer  lab recommended?

[Cleveland Clinic]

Dear ayba, Routine labwork that is monitored while a person is taking tamoxifen would include CBC (complete blood count), blood calcium levels, liver function tests.  These are often included within routine blood work.   It is possible to test for CYP2D6 mutations that may cause a person to metabolize tamoxifen differently, however, this test is not commonly used in clinical practice at this point.