Lizard wont go to bathroom

Question
My blackthroat monitor has not gone to the bathroom in almost 3 weeks now, normally he goes once or twice a week. He is still eating and drinking a lot like usual.

Is it sometimes normal for them to go this long without using the bathroom?

He has never waited this long before so I just want to make sure he is ok.

Thank you in advance for your answer :)

Answer
One of the most common causes of constipation in monitor lizards of this type is dehydration.  Dehydration can occur even when there's always drinking water available, and they're drinking it.  It happens if the humidity is too low.  Keep humidity between 60% and 70%.  These animals do not live in dry deserts in their range--they're a grassland species.

The immediate treatment is to give your monitor a good soak--put him in a bin with room temp or warmer water that comes up to just his shoulder (so he can stand in it and keep his head out of the water), and leave him there for 2 hours.  Afterward, return him to his cage with boosted humidity.  If he doesn't produce something for you while soaking, he should go within the next day or so.  If not, wait 3 days, and soak him again.  So long as he's still eating and drinking normally, nothing serious is going on--he'll go eventually.