hello and thank you for asking HCM,
I undertsand your concern. You are probably experiencing low blood pressure when you stand up, called orthostatic hypotension
. As a result, not enough blood reaches your brain, and you feel lightheaded or dizzy.
Here are some advices: move gradually from lying down to sitting to a standing position, wiggle your toes and flex your feet before you stand up. This causes the muscles in your legs to squeeze more blood back up into your heart and to slightly raise blood pressure. Try to sleep with your head higher than your feet keeps blood pressure higher.
Drink more fluids and perhaps increase your salt intake. Unless you have high blood pressure
already, this is a good idea.
Drink coffee in the morning. Caffeine boosts blood pressure.
If these advices won't help than visit your GP to make a more detailed examination.
I hope this answer was helpful to you.