Will lab tests be affected if blood is drawn through a tattoo?  I have been asked this question along with many variations of it and have not been able to find a real concrete answer to it.  I have contacted ASCP and Mayo clinic, both of which are not able to provide an answer.  I am waiting to here from Dennis Ernst as well as the Cleveland Clinic.  My question is, has anyone ever seen results that where definately affected because the venipuncture was through a tattoo?  If there is a known study that you could direct me to I would greatly appreciate it, I have spent too much time Googling this topic without information supporting or disproving it.  I know in the past we avoided tattoos so that we didn't cause scarring, which could effect the look of the piece.  We would also avoid doing Tb testing there when they were concerned with how much erythemia the site had.  I just cannot provide a clear answer, besides, thats just how it has always been.  Thank you in advance for any insite on this topic!