Thank you for your query. Yes, environmental factors can cause dehydration and result in nausea, dizziness and weakness. Appropriate amount of water is required for all bodily functions and to maintain homeostasis. Dehydration can cause you inner ear fluid to thicken (induces vertigo) can increase the concentration of your stomach fluids (gastritis, nausea), can concentrate urine (stones, infection). As you are on medications, added effect or side effects also need to be considered. Blood pressure medications work either by removing water from your body, or by relaxing the muscles in your blood vessels that cause dilation. When this occurs in the presence of dehydration, symptoms occur or may be worse. Please check with your physician before taking any new medications. Atosol (if I understand right) contains caffeine and codeine both of which can counteract the effect of your blood pressure medication. It is important to find do out the cause of your symptoms. You may require. Some dose adjustment. If it turns out to be dehydration, increased water intake (amount as suggested by your doctor) as sips throughout the day will help. Avoid going out when it is too hot, wear breathable material clothes. Have fresh juice and take cool baths. Dizziness is always better to be examined and the exact cause found. Hope this helps. Please feel free to contact us if you have any questions Wish you good health