Dry, flaky skin or lips
This is a common warning sign of dehydration. It may also indicate a more serious health problem that affects sweat gland function, such as hypothyroidism (marked by insufficient levels of thyroid hormone) or diabetes, says Roshini Raj, MD, assistant professor of medicine at the NYU School of Medicine and author of What the Yuck?! Other signs of hypothyroidism include feeling cold, weight gain, and fatigue. Diabetes symptoms include extreme thirst, frequent urination, and blurry vision.