This could be from diabetes, Cushings disease, kidney problems, liver issues etc.
If the dog is still eating well or seems even more hungry than usual for a beagle it might be diabetes.
You can read about Cushings disease a problem with the adrenal glands here
www.marvistavet.com/html/body_cushing_s_disease.html
and about diabetes here
www.marvistavet.com/html/diabetes_mellitus.html
You need to have your pet examined by your vet and maybe do bloodwork etc but the problems that can trigger this usually can be treated.
Hope this helps you!
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