If my diastolic bp is normal when sitting at rest (~80, sometimes less), is it okay that it goes to 90 when standing, or if i stop on the treadmill and take it at peak activity? it goes back to normal (or below) if i sit and rest quite quickly.

BP: It is probably OK though Id suggest performing a treadmill stress test to assess your BP response to exercise,ie normal or hypertensive,Talk to a local physician

Monitor your BP: Check BP daily & keep a log. Lifestyle modification for normal BP. Daily exercise- walking Zumba dance,yoga Salad/salmon diet- Refer to drhoffman.com for details.