The government has passed laws allowing some preventative care services at no charge. Check your insurance policy coverage and additional details at CDC.gov. You can schedule a preventative care or "wellness" visit, but remember that if your discussion goes outside the boundaries of a wellness visit and you could be charged.
Doctor offices, urgent cares, imaging centers and other such centers owned by hospitals may add an unexpected hospital "facility fee" to the bill. This article from PIRG tells more.