Greetings and welcome to justanswer,
what is your age/sex?
how long is this BP present and is it present all the time?
are you taking any drugs or medications?
At what type time this bp of 100/50mmhg is present?
do you feel any symptoms?
The blood pressure is likley to be due to the effect of the antihypertensive drug which you are taking.The Bp of 100/50 is not seriously low to be of worry since it is for a part of the day only and you do not have any symptoms as well.
You may take more of fluids during that time if you feel any symptoms.You need not worry as such because of this.
Please feel free for your follow up questions.
Any doubt then you ask me for more clarification and if you feel satisfied then click accept.