Not enough fluids in the body means the volume of blood in your body goes down. This can lead to a drop in blood pressure, which may result in the brain not getting enough blood and oxygen, leading to dizziness. The condition of low blood pressure is not always caused by dehydration.
Mild or severe headaches, and even migraines, can be triggered by not enough water because then the body doesn’t have enough electrolytes to function properly. Scientists are not exactly sure why dehydration causes headaches. One conjecture is that blood vessels may narrow, making it harder for oxygen and blood to get to the brain, causing a headache.
Rapid heart rate
An increase in heart rate is another sign you might be dehydrated, caused by the fact the body doesn’t have as much blood circulating. Blood volume is lower, and the heart beats faster to compensate, causing an increase in heart rate. This is why you may feel palpitations.