A catheter and method of making it are disclosed. The catheter includes a swellable inner element and a non-swellable outer sleeve covering an outer wall of the inner element. The inner element absorbs liquid from infusate administered through the catheter and swells in size. Outward swelling of the inner element is restrained by the non-swellable outer sleeve. The inventive catheter can be substituted for a conventional catheter that is used in an insulin infusion system.