Hi Ralph, welcome... According to the National Osteoporosis Foundation, they recommend having a dxa scan every 2 years.  That said, it also depends on how often your insurance company will pay for it and how often your Dr. thinks is necessary.  If your insurance company pays for scans more often than every 2 years you could have one sooner, but keep in mind that bone density scores don't change all that much in 2 years since bone grows slowly for most people.  Some Drs will order these tests sooner if you have extenuating circumstances that require more frequent testing.

Here's the link from the NOF explaining the frequency of dxa scans; see the link on "How Often to Repeat a BMD Test."

Good luck with this...