Brief Answer:
It is 'Postural hypotension'.

Detailed Answer:
Hi XXXXXX,
Thanks for being here on Healthcaremagic.com.
I am Dr.Ajay Panwar, a neurologist,here to answer your query.

Getting lightheadedness while sitting up or standing up from a lying position(prone or supine) is likely due to 'Postural hypotension'.

'Postural hypotension' is defined as transient fall in blood pressure(BP) while a person abruptly stands up from a lying position.It causes a relative hypoperfusion of brain tissue for a transient period of time, thus causing lightheadedness.

Its causes are-
1)Dehydration- due to any cause like fever,vomiting,diarrhea or excessive sweating.
2)Post prandial-Some people have a tendency to develop postural drop in BP,just after eating the food.
3)Heart disease- like heart failure,myocardial infarction, heart block,slow heart rate and arrhythmias.
4)Diabetes,adrenal insufficiency and low blood sugar.
5)Some neurological diseases like Multi-system atrophy.
6)Some medicines.

Precautions:
1)Please take care that while rising from the lying down position,don't stand or sit up abruptly,rather do it slowly.If you develop severe lightheadedness,then lie down for the moment.
2)Please take a lot of fluids.
3)Stop alcohol(if you take) and don't walk in hot enviornment.

If these measures do not improve the symptoms,some medicines like 'fludrocortisone' can be taken(but only under physician's guidance).

Please visit a physician so that he examine you well,see the postural drop in BP and get the necessary investigations done which are-
1)Blood sugar
2)Electrocardiogram(ECG)
3)Echocardiogram
4)Tilt-table test.

Probably, these investigations will help establish your diagnosis.Hope I have answered your query.If you still have follow-up queries,I shall be glad to answer them.Wish you good health.

Dr.Ajay Panwar,
MD,DM(Neurology)

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