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The most common cause of dizziness and darkness before eyes as soon you get up is anemia

Less oxygen goes to the brain due to anemia and it causes postural hypotension and dizziness

You are very young so take proper diet and iron supplements

Do not stress yourself

Knee crackling can be due to calcium deficiency or prolonged sitting or standing in one posture

Get your haemoglobin level , calcium level , BP check up , thyroid function tests done

It is better to consult a physician who can do whole body checkup and can send necessary investigations to the lab


If you are having heavy periods consult a gynecologist because anemia can be due to heavy flow during menses

Any further query is most welcome

Best wishes

Take care

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