I get high BP when I stand and low when I lay. Today I'd done 10mins or so gardening and then had to come inside and rest but decided to check out what this exercise (I rarely do gardening) had done to my BP (as I expected it to be high due to having been standing just before and would rapidly within minutes, come down while I rested). As expected, my first reading was high (diastolic 95) then thou I started getting shaky (my head was starting to shake) so took my BP again to see how it had shifted. After it erroring out 4 times straight, after about 5mins, I finally got another reading and my dystolic was now at only 47 ..guess that explains why I was starting to get shakes (my systolic was fine..its the dystolic I have more issues with). Are BP drops like that when resting any cause for concern? Is there at any point of low BP one should worry about? (I noticed a similar sudden fall like this too a few weeks ago. I rarely take my BP so it could be doing this quite a bit).