It’s no surprise that drinking enough water is important. After all, the human body is about 60 percent water. According to the Journal of Biological Chemistry, the lungs are made up of about 84 percent water, kidneys are 79 percent, and the heart and brain are 73 percent. Even "bone dry" bones are 32 percent water.
Growing up, most of us were told to aim for eight 8-ounce glasses of water every day but, as Healthline pointed out, the origin of this guideline is unclear and it has not actually been supported by scientific research. The Institute of Medicine (IOM) recommends women aim for 91 ounces (2.7 liters) of fluids each day, while men should get 125 ounces (3.7 liters) daily. The IOM noted, however, that not all of your fluid intake has to come from plain water, but "all beverages and food." And everyone’s exact hydration requirements vary. Factors such as exercising, temperature, illness, and pregnancy can all impact fluid needs.
While every person’s needs are slightly different, the dangers of dehydration are universal. We all know the obvious symptoms of dehydration, such as thirst, a dry mouth, and dark-colored urine. But when it comes to chronic dehydration, there are many other subtle ways your body can communicate that it needs more fluids.
If you’re not drinking enough water, you may experience weight gain
If you’re not sure why you’ve put on a few extra pounds, it could be because you’re not drinking enough water. As registered dietitian Megan Wong of AlgaeCal told Health Digest, "Drinking water increases feelings of satiety, meaning a feeling of fullness. This could be why researchers have found a link between obesity and inadequate hydration."
One study, for example, led by Dr. Tammy Chang and published in the Annals of Family Medicine in 2016, examined the health habits of over 18,000 adults and found that those who weren’t well hydrated were more likely to have an elevated body mass index (BMI).
One reason for the connection between hydration and BMI may be the fact that people often misinterpret thirst as hunger, thus filling up on calories when what they really need is fluids. According to the Polycystic Kidney Disease Foundation, 37 percent of individuals mistake thirst for hunger. Registered dietitian Trista Best explained that this mix-up in signals can cause "late-night binge eating, overeating at meal times, and chronic snacking." The next time you think you’re hungry, Wong suggested drinking a glass of water before immediately reaching for a snack.
If you’re having heart trouble, you may not be drinking enough water
Not drinking enough water can have major consequences for your cardiovascular health. According to The Heart Foundation, "When you are dehydrated your blood volume, or the amount of blood circulating through your body, decreases. To compensate, your heart beats faster, increasing your heart rate and your blood pressure." Your blood also retains more sodium when you’re dehydrated, thus thickening your blood and making it more difficult to circulate through your body.
ScienceDaily noted that dehydration increased individuals’ risk for cardiac disease and arteriosclerosis (the hardening of artery walls), even among young, otherwise healthy individuals. In the article, Stavros Kavouras, associate professor and coordinator of the Exercise Science Program at the University of Arkansas, argued that when it comes to heart health, dehydration is as bad for the body as smoking a cigarette.
Alarmingly, even very mild dehydration can be bad for your heart. Kavouras explained, "The degree of dehydration when these changes occur is at less than 2 percent dehydration, which is around the threshold when people start feeling thirsty." Heart disease is the leading cause of death in the United States, and while there are many contributing factors, dehydration is an easily preventable one.
If your blood pressure is out of whack, you may not be drinking enough water
According to Healthline, dehydration can both raise and lower blood pressure, both of which can be dangerous if left unchecked. Without enough fluids in your system, blood volume decreases, which lowers blood pressure. On the other hand, dehydration-induced low blood volume and an increased concentration of salt in the bloodstream trigger the release of the hormone vasopressin. This hormone causes narrowing and tightening of blood vessels that, in turn, lead to an increase in blood pressure.
The Mayo Clinic noted that a blood pressure reading below 90/60 mm Hg is generally considered low. Low blood pressure (hypotension) can cause many symptoms, including dizziness and fainting, fatigue, blurred vision, and nausea. If it drops too low, your organs won’t receive the oxygen and other nutrients they need, resulting in life-threatening hypovolemic shock.
High blood pressure (hypertension), on the other hand, is a major risk factor for stroke and heart disease. It’s also a common problem in the United States, affecting approximately 103 million Americans (almost half of U.S. adults), according to the American Heart Association.
Constantly exhausted? You may need to drink more water
If you constantly feel tired and it’s a struggle to make it through your day, you’re not alone. In 2017, the group Occupational Health & Safety, citing research conducted by the National Safety Council, reported that 76 percent of survey participants felt tired at work, 53 percent felt less productive, and 44 percent had difficulty concentrating. While there are many reasons you may be feeling fatigued and distracted, dehydration is an often overlooked cause.
A 2012 study published in The Journal of Nutrition found that even mild dehydration of only 1.36 percent led female participants to feel more "fatigue-inertia" and made tasks seem more difficult. Not getting enough fluids also impacts sleep quality. According to the Sleep Foundation, dehydration can make you feel sluggish during the day, but it can also negatively affect your sleep, making you even more tired the next day. Going to bed dehydrated can even worsen snoring, which is disruptive to a good night’s sleep.
If you’re worried that your morning coffee is doing more harm than good, though, you can relax. According to Harvard Medical School, drinking caffeine in moderation does not lead to excessive fluid loss and dehydration.
Are muscle cramps a result of not drinking enough water?
Muscles are made up of about 80 percent water, so it makes sense that dehydration could lead to muscle cramps, especially when it accompanies strenuous exercise. The Mayo Clinic, which listed dehydration as a risk factor for muscle cramps, explained, "Fluids help your muscles contract and relax and keep muscle cells hydrated." The Cleveland Clinic also cited dehydration as a possible cause of nighttime leg cramps.
However, not everyone agrees that dehydration leads to muscle cramps. One 2013 study published in the British Journal of Sports Medicine concluded that a lack of fluids did not change how likely study participants were to experience muscle cramps. The authors argued that neuromuscular control — the cooperation between your body’s muscles and nerves — may play the most important role. Another study, led by Dr. Wing Yin Lau and published in 2019, found that it was actually drinking water after being dehydrated, not the dehydration itself, that caused muscle cramps. The study’s authors attributed this to the change in the concentration of electrolytes that drinking water caused. As such, you may find that drinking water with electrolytes may help.
Not drinking enough water can impair brain function
Dehydration may be at the heart of your persistent brain fog. As nutritionist Mira Dessy told Health Digest, "Often overlooked is the link between dehydration and reduced cognitive performance. It doesn’t take much — even as little as one percent dehydration can cause changes in your ability to pay attention and remember things."
Interestingly, dehydration doesn’t appear to affect all areas of brain function to the same degree. As a 2016 conference paper authored by Matthew T. Wittbrodt of Emory University and Melinda Millard-Stafford of Georgia Tech revealed, "High-order cognitive processing (involving attention and executive function) and motor coordination appear more susceptible to impairment following dehydration." Lower-order mental processing (such as reaction time) was much less disrupted by the lack of fluids. The researchers noted that dehydration’s effects on the brain were particularly noticeable once individuals had lost more than two percent of their body’s water.
If you’re always constipated, you may not be drinking enough water
According to the Mayo Clinic, constipation is defined as "having fewer than three bowel movements a week." While almost everyone experiences constipation from time to time, for some people constipation becomes a chronic condition, resulting in weeks or even months of infrequent or painful bowel movements. UCLA’s Gail and Gerald Oppenheimer Family Center for Neurobiology of Stress and Resilience estimated that between 2 and 28 percent of people in North America suffer from chronic constipation.
Although constipation is often blamed on a lack of dietary fiber, M. J. Arnaud of Nestlé Water Institute noted that hydration levels also play a critical role. Dehydration was cited as a potential risk factor for constipation in Arnaud’s 2003 paper published in the European Journal of Clinical Nutrition. Additionally, it was revealed that "fluid intake and magnesium sulphate-rich mineral waters were shown to improve constipation" — at least in healthy babies.
U.S. News & World Report advised drinking plenty of water as the first step to conquering constipation. According to the publication, "When your body is properly hydrated, less water will be withdrawn from the colon." This ensures "soft and easy to pass" stool.
If you don’t drink enough water, you risk getting kidney stones
Kidney stones (aka renal calculi) are hard deposits of minerals and salts that form in the kidneys. They can be quite painful to pass and may even require surgical removal. According to the University of Wisconsin-Madison, the incidence of kidney stones is on the rise, especially among women. Approximately 13 percent of men and 7 percent of women will experience kidney stones at least once in their life, and once you’ve had kidney stones, there’s around an 80 percent chance you’ll have them again in the next 10 years.
The Urology Care Foundation listed dehydration-induced low urine volume as a major risk factor for developing kidney stones. The foundation explained, writing, "When your urine volume is low, urine is concentrated … . Concentrated urine means there is less fluid to keep salts dissolved." As such, upping your water intake will help.
If you’re experiencing any of the symptoms of kidney stones, including a sharp pain in your back or lower abdomen, pain while urinating, or blood in your urine, it’s important to see a doctor and, of course, drink more water.
Not drinking enough water could make you more susceptible to UTIs
According to the U.S. Department for Health and Human Services, 50 percent of women will get at least one urinary tract infection (UTI) in their lifetime. This bacterial infection can cause many unpleasant symptoms, including painful and frequent urination, fever, and fatigue.
Your level of hydration is one of the factors that influences your chances of getting a UTI. In an article written for Harvard Medical School, Huma Farid, an obstetrician-gynecologist, highlighted research demonstrating that women who drank the most water (their "usual amount of fluids plus an additional 1.5 liters of water") had 50 percent fewer episodes of recurrent UTIs than women who didn’t increase their fluid intake. She noted that this is most likely due to the fact that drinking enough water encourages frequent urination, which helps flush bacteria out of the body. It’s no surprise, then, that UCLA Urology listed "not drinking enough fluids" as a risk factor for UTIs.
When it comes to your hydration level, your urine may be the best indicator of whether or not you need to drink more fluids. According to Healthline, urine the color of lemonade or light beer indicates optimal hydration, while anything darker is a sign of dehydration.
If you’re always getting sick, you may not be drinking enough water
Advice to drink a glass of orange juice or eat chicken noodle soup to help recover from a cold may have less to do with the nutrients in these homeopathic remedies and more to do with the fact that both contain a significant amount of water. Nutritionist Lisa Richards told Health Digest, "Drinking enough water is vital to eliminating toxins from the body by fueling the organs with necessary liquid to aid in filtering waste. Dehydration causes an accumulation of toxins in the body, resulting in increased susceptibility to illness and taking longer to recover."
Houston Methodist Hospital highlighted how important proper hydration is to a well-functioning immune system, writing, "A fluid in your circulatory system called lymph, which carries important infection-fighting immune cells around your body, is largely made up of water. Being dehydrated slows down the movement of lymph, sometimes leading to an impaired immune system."
According to WebMD, the lymphatic system acts as a filter for the body, removing waste products from cells and trapping foreign invaders like bacteria and viruses in specialized tissue known as lymph nodes. It also produces lymphocytes, a type of infection-fighting white blood cell.
Not drinking enough water can make your allergies worse
If your allergies have been acting up more than usual, it may be a sign that you need to drink more water. In an interview with CBS News, Dr. Neeta Ogden, an allergy specialist and spokesperson for the American College of Allergy, Asthma and Immunology, explained the connection, saying, "Studies have shown that when you’re dehydrated your body produces higher histamine levels and that drives allergies. When you get dehydrated you could run [the] risk of making your symptoms worse."
According to WebMD, histamines are chemicals produced by the immune system that play the starring role in an allergic reaction. Once you’ve been exposed to a trigger (such as pet dander or peanuts), histamines travel to wherever the allergen was detected, causing inflammation. This inflammation produces the telltale signs of an allergy, such as itching, congestion, and swelling. It also signals other immune cells to attack and destroy what is actually a harmless foreign substance.
Ogden pointed out that the decongestants often used to treat allergies can dry people out, making dehydration even worse. She recommended adding electrolyte powder to plain water to boost its allergy-fighting abilities.
Achy joints? You may need to drink more water
If you thought arthritis was a condition that only affected older people, think again. According to the Arthritis Foundation, nearly one in three Americans between the ages of 18 and 64 are living with arthritis or arthritis symptoms. Of individuals with the condition, the Centers for Disease Control and Prevention (CDC) reported about 50 percent have persistent joint pain and one in four have severe joint pain.
Interestingly, not drinking enough water can make joint pain worse. As registered dietitian Trista Best explained to Health Digest, "The joints contain cartilage that prevents the bones from grinding and rubbing together. Cartilage is roughly 80 percent water, and when you aren’t drinking enough water it becomes less hydrated. This leads to joint pain as a result of increased friction."
In addition to plumping up cartilage, water is also the primary component of synovial fluid, according to the Tucson Orthopedic Institute. This fluid surrounds and protects the bones and cartilage of the joint. The institute also noted that water helps maintain the muscles that support joints. Dehydration can reduce muscle tone by reducing a muscle’s ability to contract, thus making the joint more unstable and prone to injury.
If you have dry skin, you may not be drinking enough water
Oftentimes, our skin is a reflection of what’s going on inside of our bodies — and dehydration is no exception. In fact, skin turgor is often used to determine whether or not someone is dehydrated. As BBC Future explained, "[Turgor] is a measure of how fast it takes the skin to return to normal if you pinch some skin and lift it up. If you are dehydrated your skin will take longer to get its shape back."
"Normal skin owes its soft, pliable texture to its water content," according to the Merck Manual. When water is lost, it becomes irritated, rough, and scaly and may peel or itch. Although dry air is a common cause of dry skin, avoiding dehydration is also an important part of supporting skin health from the inside out.
In an interview with Harper’s Bazaar, dermatologist Justine Hextall explained that well-hydrated skin appears plump and reflects light better, giving it a glowing appearance, while dehydrated skin is less elastic and appears "dull and lifeless." She cautioned that for those with naturally dry or sensitive skin, dehydration can be particularly damaging.
Not drinking enough water can cause frequent, painful headaches
Dehydration is a common — but completely preventable — cause of headaches. According to Medical News Today, "When the body is dehydrated, the brain can temporarily contract or shrink from fluid loss. This mechanism causes the brain to pull away from the skull, causing pain and resulting in a dehydration headache." This pain can range from dull to intense and may be felt on the front, sides, back, or all over the head.
Dehydration is also a common migraine trigger. In a 2020 study published in the Journal of Clinical Neuroscience, a team of researchers in Iran examined the hydration habits of over 250 female migraine sufferers aged 18 to 45. The researchers found a correlation between low water intake and frequent migraine attacks. They also noted that women who drank less water tended to have more severe and longer-lasting migraines than those who drank more water.
If dehydration can cause headaches, it seems logical that drinking extra water could improve symptoms. That’s exactly the conclusion reached in a pilot study conducted in 2005 and published in the European Journal of Neurology. It found that participants who drank an extra 1.5 liters of water over a 12-week timeframe had shorter, less severe headaches. Drink up!