That's not technically true. They do go to the doctor if they are ill. Some may believe that through them God will work that they will be cured.

A person who professes to be a student of Christian Science will usually rely on spiritual means alone for physical healing. The "spiritual means" are effective and reliable prayer.. He has learned by experience that he can trust God's healing power wherever he is - no matter how severe the physical problem seems to be. Persons who have had healing by spiritual means alone tend to stay with what they know they can rely on, and are not likely to take drugs. That is why Christian Scientists do not normally resort to doctors or drugs. They are learning that they can trust God for all their needs, and they feel that they are healthier and happier for it.

Although there is no church doctrine forbidding the use of medical treatment, Christian Scientists generally turn to Christian Science treatment as their first resort for healing any illness or problem in their lives. This is often due to their own experience or awareness of successful healings using this spiritual system. In many cases a Christian Science Practitioner is called to prayerfully “treat” the case. This is form of prayer that clarifies the God-given spiritual identity of the patient. It seeks to look beyond the view of a physical being to gain a tangible realization of one’s spiritual selfhood as the flawless creation of a perfect and all-powerful God. Healing takes place as an effect of gaining an inspired sense of divine Love’s (God’s) presence and power in our life – even to the point of feeling that our life and health is the very outcome or reflection of God’s perfection. The particular spiritual ideas, and inspirations that might be shared during a Christian Science treatment are intended to spiritualize thought, thus anything that would focus on a material, or bio-chemical view of being tends to counter this spiritualization. Thus, the effectiveness of Christian Science treatment is hampered when material medication or treatment is also being administered.