Hello Welcome to HCM. By your description it looks like you have orthostatic hypotension. It happens when you get up suddenly from a lying position which leads to fall in BP and leads to dizziness and fainting. You can measue your BP in lying position and then in sitting and standing position. If the higher reading (systolic BP) falls than more than 20 mmhg on sitting or standing then you have postural or orthostatic hypotension. You have not mentioned here other medical issues if you have any. Some patients who are on diuretics or water pills, some anti hypertensive medications have these side effects. See your doctor and ask him whether you are on any of these medications. This repsonse can happen due to dehydration also, so if you are a kidney patient or generally drink less water, you can develop orthostatic hypotension. Please increase your water intake to 2-2.5 lit daily (provided you are not a heart or kidney disease patient). Also precautionary measures should be taken like getting up slowly from lying position and sitting for a minute and then get up.. wait for a minute and then walk. This will help the body adapt to the posture. Sometimes pooling of blood in the legs also can cause these symptoms. You can also use leg stockings to increase the flow of the blood back from the legs into the heart which can also help in your condition. If despite these measures you still have these complaints which severely affect your lifestyle then you can take tab midodrine 2.5 mg up to three days times a day. Remember this medication should be taken only if above measures are not effective and not as a first line of treatment. Wishing you good health. Regards