The short answer is, absolutely not! CareCart loads on the Shopify store asynchronously. This means that it does not block the other parts of the page that are in downloading phase.
CareCart uses a global CDN to deliver all the images and stylesheets which is not placed on the critical render path of your store. We comply with the strict coding standards of Shopify apps store, this is why CareCart does not slow down the page load speed of your store.