Hello,
Good afternoon,
At first to avoid giddiness, have a glass of buttermilk with salt or lemon juice with salt to normalize your BP level.
Next Steps
As you are young and if you don't have any previous medical issues, then no need to worry about this. Just take normal salt in your meals. But if this occurs repeatedly don't ignore, its better to consult a physician. It might also depends on your region's climatic condition and your lifestyle.
Health Tips
If you are from hot climate region have plenty of liquids(juice or coconut water or soup or anything), water level in your body may also affect bp levels. If you need consultation plz do contact me. Have a healthy day!!
Thank you 🙂