you should not take at the same time are Creatine + L-Glutamine. You should not take Creatine and Glutamine at the same time, because Creatine and Glutamine depend on many of the same substrate carriers and co-transporters. When the two are competing with one another for the same carriers, one wins and one loses.
Solution: Simply take them with 2 hours apart. Most bodybuilders are taking L-Glutamine before they train and before they sleep, and Creatine after they train and first thing in the morning. So this way, they give their bodies plenty of time to absorb each one of these separately. For others that train after their breakfast, if you take Creatine only once per day, take it after your training, and on the days you don't train, simply take your second dosage 2-3 hours after your morning L-Glutamine serving, or 2-3 hours before your last L-Glutamine serving.