What precautions and medicines i need to take while going to a very high altitude leh-ladakh?

Ascend slow; Diamox (acetazolamide): Take your time at going into higher altitude to prevent altitude sickness and more importantly high altitude pulmonary and/or cerebral edema (swelling). You likely want to take a medicine 1-2 days prior to and during your trip called diamox (acetazolamide). You will need a prescription from your doctor for this. If you start feeling very short of breath or lightheaded or confused descend some immediately.

Altitude Sickness: Leh, altitude 11500 ft (3500 m), is at the defined border between high and very high altitude. Low o2, pulmonary and cerebral edema are the main concerns with altitude sickness, which is made worse by rapid ascent. Precautions and treatment will depend on your health. You should consult with your physician about specifics.