1. Stop and rest where you are.
2. Don’t go higher for at least 24-48 hours.
3. If you have headache, take Ibuprofen or paracetamol.
4. If you are sick take anti sickness medication, like promethazine.
5. Make sure you are drinking enough water.
6. Avoid exercise, alcohol and smoke.
7. If you feel better then go up, if felt worst then go down.