You wake up dehydrated because your body loses water overnight through breathing, sweating, and lack of intake, leading to a deficit by morning, especially if you don't drink enough during the day, consume diuretics like alcohol, have a dry mouth from mouth-breathing, sleep in a hot room, or have certain health conditions like sleep apnea or diabetes. Even in cool weather, we lose fluid from respiration, and avoiding drinks before bed to skip bathroom trips worsens this.
When you sleep, your body naturally loses fluids and electrolytes in several ways. When you snore or breathe through your mouth at night, moisture in your nose and mouth gradually evaporates, causing mild dehydration that can result in waking up thirsty.
How to Prevent Dehydration During Sleep
Insufficient Electrolytes
As we already discussed, maintaining bodily hydration requires electrolytes. While water certainly helps with fluid balance, your body can still struggle to retain water if you're not getting enough electrolytes—and that often equals dehydration.
Dehydration is a deficiency of water in the body. Vomiting, diarrhea, excessive sweating, burns, kidney failure, and use of diuretics may cause dehydration. People feel thirsty, and as dehydration worsens, they may sweat less and excrete less urine.
Concussion, menopause, and hypothyroidism all have symptoms similar to being dehydrated.
Symptoms of vitamin B12 or folate deficiency anaemia
Symptoms of dehydration
The body may lose too much fluid due to diarrhea, vomiting, severe blood loss, or high fever. Lack of a hormone called antidiuretic hormone (ADH) can cause the kidneys to get rid of too much fluid. This results in extreme thirst, dehydration, and chemical imbalance of the blood.
An electrolyte panel is a blood test to measure electrolytes (minerals) in your blood. An electrolyte imbalance may be a sign of a heart, lung or kidney problem. Dehydration also causes electrolyte imbalances.
The 3-2-1 bedtime method is a simple sleep hygiene strategy: stop eating 3 hours before bed, stop working 2 hours before bed, and stop using screens (phones, tablets, TVs) 1 hour before sleep, helping your body transition to rest by reducing stimulants and digestive load for better sleep quality. A more detailed version adds 10 hours (no caffeine) and 0 (no snoozing) for a 10-3-2-1-0 rule.
Milk is more hydrating than water
The same can be said for oral rehydration solutions that are used to treat diarrhea. Those contain small amounts of sugar, as well as sodium and potassium, which can also help promote water retention in the body.
By drinking water when you wake up, the blood flow to your brain is improved, helping you stay more alert. Flushes out toxins – As you sleep, your body carries on working to repair and regenerate cells. A glass of water in the morning will help your kidneys flush out your body's waste and toxins more effectively.
Greater thirst and more urination
Being very thirsty and urinating often are common diabetes symptoms. In people who have diabetes, extra sugar — which also is called glucose — builds up in the blood. This forces the kidneys to work overtime to filter and absorb the extra sugar.
Is it dehydration or something else?
Dehydration, which happens when the body loses more fluids than it consumes, can cause a range of symptoms including thirst, weakness, light headedness, fainting and decreases in urine output or increases in its concentration (darker colored urine).
Dehydration occurs when you don't have enough fluid in your body. It can cause symptoms like thirstiness, dry mouth and headache. Severe dehydration can be life threatening, especially for babies, young children and older people. You can prevent dehydration by drinking enough fluids.
You can test for dehydration at home with the skin turgor test (pinching skin on your hand or abdomen; slow return means dehydration) or by checking urine color (darker means more dehydrated) and observing for other signs like a dry mouth, fatigue, or lack of tears in children. While simple, these methods aren't always precise, especially in older adults, so see a doctor for severe symptoms like skin tenting or persistent vomiting.
Medicines that make dehydration more likely are:
9 healthy and hydrating alternatives to water
B12 deficiency can trigger specific food cravings, most notably for meat, fish, or eggs, as the body seeks animal-based sources to replenish the vitamin, especially in those on vegetarian/vegan diets or older adults. While cravings for sugary or salty foods can also signal general B-vitamin issues, the distinct urge for protein-rich animal products is a key indicator, but professional testing is crucial for confirmation.
Cutaneous manifestations associated with vitamin B12 deficiency are skin hyperpigmentation, vitiligo, angular stomatitis, and hair changes. A diagnosis of vitamin B12 deficiency is often overlooked in its early stages because these signs are not specific to vitamin B12 deficiency alone.
Possible symptoms of anemia include: