Brief Answer:
may be due to orthostatic hypotension

Detailed Answer:
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Dizziness on standing may be due to: (1)orthostatic hypotension
(2)BPPV
(3)meniere's disease
(4)vestibular neuronitis

Dizziness on standing may be related to a fall in blood pressure when a person moves from a sitting/lying to standing position. This is called orthostatic hypotension.

This is diagnosed by checking the blood pressure in the sitting and then in the standing positing. If there is a signficant drop then this is diagnosed.

Orthostatic hypotension may be related to: not using enough fluids, side effect of medication, heart disease

If there is a specific heart problem causing it then this is treated.Other aspects of treatment include drinking enough water (this helps with blood volume and blood pressure) and also standing very slowly to give the blood pressure a chance to normalize.

In some cases special stockings may be needed and medication.

Dizziness on standing may also occur in other conditions such as BPPV, meniere's disease and vestibular neuronitis. These are conditions affecting the inner ear which plays a part in controlling a persons balance.

These conditions would normally cause a feeling as though the room or the person is spinning.

The treatment varies according to which one is present.

Summary: (1) may be orthostatic hypotension (low bp on standing). Doctor would need to confirm and determine cause
Treated by fluids, standing slowly and addressing particular cause

(2)may also be related to inner ear conditions, none of which are life threatening but can be difficult to tolerate.
Treatment varies according to exact cause

I hope this helps, feel free to ask any other questions

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