Brief Answer:
few things to consider..

Detailed Answer:
Hello XXXX, Welcome to HCM,
I've gone through your query and understand your concern,

First of all, please note that, this symptom can be observed due to physiological variation of blood pressure observed during postural changes (specially after getting up from lying down position), known as postural hypotension.. to overcome this, it'll be helpful not to sit up and get up suddenly from the bed..take time, 10 min in semi-recumbent position, then getting up slowly and take another 10min after sitting up, drinking a large glass of water after getting up will help..

Secondly, if you're hypertensive and/ on any blood pressure lowering medications or any water pills then it's the right time to get yourself checked up by your Doctor and titrate the dosage accordingly..

If you're not hypertensive, then it's even more important to get your blood pressure checked at serial intervals in different postures along with 12 lead EKG and few relevant investigations (eg. Hemogram, serum electrolytes sp. Sodium, Potassium and Renal function assay)..management will be done according to the findings..

There's another possibility of BPPV or Benign paroxysmal positional vertigo, a disorder due to inner ear system, which can also present as the same, but it should be suspected only after ruling out the cardiological concerns..

So please get examined by your doctor and investigated accordingly for those necessary findings, not to worry, but it's important to get them done without delay to avoid any future complications..

Let me know how you stay in the due course..

Take Care
Kind Regards

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