When i'm sitting down my hr is 69. upon standing it gets to 99 and when i start walking it gets into the low 100's. what could be wrong?

?Dehydrated: One possible answer is that you could be "intravascularly volume depleted" meaning somewhat 'dehydrated.'Try increasing your fluid intake, replacing electrolytes etc. and see if you feel more refreshed and energetic and your HR goes more to normal. You have a Positive "tilt test" by HR standards, so if this does not help...you need to see the Dr (best-cardiologist) for a routine eval of the issue.