How low does a person's diastolic pressure have to be to be considered too low?

Probably not: A low diastolic blood pressure with a normal diastolic blood pressure often is of no significance. In some people, their blood pressure sounds can be heard all the way down to 0 when nothing is wrong. A large difference between systolic and diastolic pressures (wide pulse pressure) may indicate aortic regurgitation, however. Check with your doctor.