@vashti, Welcome to Mayo Connect. We are an online community of patients who share our experiences to help each other as we support and encourage each other. This is a good question.

Whenever my tac levels, or anything, goes out of my normal, I begin to self examine any possible causes. Since you have identified essential oils as a possible culprit, I highly urge you to STOP and to have a follow-up lab to find out if the essential oils are causing this. Remember that your transplanted organ needs a targeted level to prevent rejection. Each of us has an assigned target level, determined by our transplant team.
The only way you will know for certain is to quit the essential oil, ane get a repeat lab.

Has your transplant team ordered a repeat lab and tacrolimus test? Have you stopped the essential oil?