Stress underlies all disease and any additional stress should be avoided. Seeking a reading in the hope of finding relief from a medical issue may provide some comfort, but it will depend very much on the reader. If you already know your tarot reader then you will probably have built up some trust over time. If you can ask questions geared around possible choices which could help relieve stress then this would be the most constructive use of the reading. But any element of fear or desperation around a health issue can cloud a reading. It would be wiser to take a meditation class and practice relaxation techniques. In this way you can learn to make a connection to your higher self and access the self-healing and inner wisdom that is available to everyone.