If your mouth feels drier and stickier than usual, it’s high time to rehydrate. According to experts at the Baylor College of Medicine in the US, a general rule of thumb is “if you’re thirsty, you’re already dehydrated.”

A common cause of headaches and migraines is dehydration. When your body is dehydrated, all your muscles and tissues get affected, including the ones in your brain. This causes brain tissue to contract, triggering pain receptors in the area.

There is less blood flow to the brain and your heart rate speeds up when you’re dehydrated. This causes you to feel giddy or faint, especially if you are standing for a long time, or if you change positions suddenly.

Approximately 50-65 per cent of your body is made up of water, and you need it to function optimally. Dehydration can also cause you to feel sluggish, and lead to poor concentration.

A lack of water affects your entire cardiovascular system too, and can lead to lower blood pressure and a quicker pulse.

When you’re dehydrated, your body does everything it can to conserve water, and this leads to less frequent toilet trips. The National Health Service (NHS) in the UK also qualifies not passing urine for eight hours as a symptom of severe dehydration.

This is a symptom of severe dehydration, and immediate medical attention should be sought. In serious cases, the patient may even become unconscious.