According to the Iowa Implied Consent Law:

Under Iowa's Implied Consent Law, any peace officer may ask you to submit to a breath, urine, or blood test if the officer feels you may be driving under the influence of alcohol or drugs. This applies to both resident and non-resident drivers. If you take the test and fail, or you refuse to take the test, your license can be taken away on the spot.
DMV Writen Test Logo