What are the rest of your water parameters? Looking at only one result, in a vaccum, leads to chasing numbers. I'd check magnesium, if it's low bring it up. If it's high water change till it's right (test your change water before you add it). Once your magnesium is set right then recheck your alk, if it's still high, then check your calcium. It'll probably be low, add it up and that should bring your alk down. If, the calcium is high then I'd look at the water you're using and the salt you're using.
Alk and calcium have an inverse relationship, magnesium determines how tight that relationship is.
As was said elsewhere on this site, check and record ALL your water parameters for a few weeks until you see the paterns of life cycle that your particular tank goes through. Once you see the whole picture then you can make small adjustments to stabilize it for the long haul. Makeing knee-jerk reactions to any one particular test probably isn't the best aproach to long term sucess. If things look really screwy, or something is at a dangerous level, water change, water change, water change, but, be sure the water you are changing with is good with all parameters. That's why RO warter is so important. It gives us a known start point to add our salt mix too.
Hope that didn't sound like a ranting lecture. Just trying to be informative and give reasons to why to do things, rather than just "do this or that".