All this is subject to correction. I haven't bothered to look it up.

If you are suspected of drunk driving in Colorado, you must submit to either a blood or breath test or lose your license for one year. If you are suspected of driving under the influence of drugs, you must submit to a blood test or face the same civil penalty. If you refuse a test, prosecutors will use this in court as part of their DUI case for your guilt. My own personal belief is that no test that comes back positive for any amount of THC will be exculpatory. I would refuse the test and trust my lawyer to win in court. Also, I have other compelling reasons: a DUI conviction would have professional consequences and since I seldom drive, I wouldn't be seriously inconvenienced by the loss of my license.