You do not need to stop your prescribed medication before your Lucis blood test. Keep taking it as prescribed, and do not stop or change it without discussing it with your doctor first.
If you take a prescribed treatment (for example for the thyroid or blood pressure), it helps to keep a note of it. Some treatments can influence certain biomarkers, and that context is taken into account when your results are interpreted.
Supplements are different: vitamins, minerals, omega-3 and similar should be stopped 72 hours (3 days) before your test. See When and which supplements should I stop before my blood test?.