Decreased frequency of urination and decreased volume of the excreted urine in the morning are practically the only reliable symptoms of mild dehydration. Mild dehydration has no significant effect on the urine color, which therefore remains normal (translucent or light yellow) 1.
- Thirst is typical but unreliable and relatively late symptom of dehydration. Thirst usually appears only when you lose 1-2% body weight due to dehydration 4,34.
- You can be mildly or severely dehydrated and may or may not be thirsty. Older people and children are often less aware of thirst.
- You may not be dehydrated but can feel thirst because of having dry mouth, eating salty food, seeing an attractive drink or due to psychological reasons (psychogenic polydipsia).
- When you do not eat and drink you may feel no thirst because you do not consume any salt, which triggers thirst.
- Some people may confuse thirst for hunger 23. This is why it may help if you drink some water before meals — it may make you less hungry and thus prevent weight gain 38.
- Dry mouth is an early but unreliable symptom of dehydration.
- A person can be dehydrated but having moist mouth when thinking about food (increased salivation).
- A person can be normally hydrated but having dry mouth due to dry air, breathing through the mouth, anxiety and other strong emotions and in certain conditions, such as inflammation of parotid glands and Sjögren’s syndrome 3.
- Dry mouth in the morning after drinking alcohol at night is not necessary a symptom of the whole body dehydration but possibly only of dehydration of the mouth mucosa.
Other Typical Symptoms
- Feeling hot 37
- Slight tiredness, less energy
- Slight anxiousness, especially in women 4
- Decreased or increased appetite (hunger)
- Mild headache 4
First Warning Signs
Mild dehydration may cause no visible signs.
- Sudden loss of weight (within hours to few days) by 1-3% (1.5-4.6 lbs in a 154 lbs adult or 0.7-2.1 kg in a 70 kg adult) is the only reliable sign of mild dehydration 1.
- Slightly increased heart rate 1
- Skin turgor test: skin recoil after pinch and release can be slightly delayed (for less than two seconds).
In moderate dehydration, few or all the following symptoms can be present:
- Less frequent urination, burning urination, low amount of excreted urine; urine color may range from yellow to almost black (tea-colored). Urine is dark due to increased concentration of bilirubin.
- Thirst, possibly waking you up at night, but sometimes no thirst at all
- Dry mouth and lips
- Bad breath (halitosis) 16
- Poor appetite 23
- Dizziness and lightheadedness, balance problems 17
- Fatigue, drowsiness, sleepiness or insomnia 17
- Difficulty concentrating, impaired memory 17
- Nervousness (jitters) 17
- Moderate headache
- Stomach cramps (in food poisoning, gastroenteritis) 20
- Sensitivity to light and noise 17
- Anxiety, depression 3
- Constipation and associated bloating
- Thirst and waking up and drinking at night (polydipsia
- Jet lag 24
- Morning sickness in pregnant women
- Sudden loss of 3-6% body weight: 4.5-9 lbs in a 154 lbs adult or 2-4 kg in a 70 kg adult 1.
- Dry mouth mucosa 1, white or yellow tongue 28
- Dry, sunken eyes; dark circles or bags under the eyes due to localized edema 26
- Skin turgor (elasticity): recoil after pinch and release delayed for up to two seconds 8
- Capillary refill time: 2-4 sec 1
- Increased heart rate (tachycardia): faster than usual for an individual at rest (>60-100/min)
- Increased breathing rate (>28/min) 1,6
- Pulse: weak, thready 1
- Blood pressure: normal, but decreased upon raising up (orthostatic hypotension, systolic pressure drop by 10-15%) 1,6
- Low-grade fever 6
Dehydration in adults is considered severe when it results in more than 6% loss of body weight 1,5.
Symptoms of Severe Dehydration
- Less frequent or no urination; dark yellow, orange, amber, brown, tea-colored or almost black urine
- Painful urination
- Extreme thirst, but sometimes no thirst
- Apathy, lethargy, exhaustion, irritability
- Malaise, hangover-like feeling
- Dizziness, vertigo
- Very increased heart rate (possibly over 140/min), pounding heart (palpitations)
- Increased breathing (hyperventilation) or decreased breathing (respiratory depression), difficulty breathing (dyspnea)
- Tingling and numbness in fingertips (due to hyperventilation)
- No sweating despite high ambient temperature, dry itchy skin 30
- Severe headache or migraine 14,15
- Scratchy, itchy throat 23
- Body aches: stomach pain, back pain, leg pain 19
- Anorexia 13
- Problems with eyesight: blurred vision, temporary vision loss (blindness)
- Chest pain
- Lower back (flank) pain in acute kidney failure due to dehydration 29
- Confusion (may resemble dementia), delirium, hallucinations
- Fainting, passing out (unconsciousness), coma.
- Sudden loss of more than 6% of body weight: more than 9 lbs in a 154 lbs adult (more than 4 kg in a 70 kg adult) 1.
- A severely dehydrate person usually has pale, wrinkled, dry and cool skin.
- In heat exhaustion and hypovolemic shock, the skin is usually pale or mottled, sweaty and cool 10. In hypovolemic shock, the fingertips may be bluish (cyanosis).
- In heat stroke due to hot weather the skin is pale or flushed, hot and dry 9,21.
- Reduced skin turgor (elasticity): skin recoil after pinch and release can be delayed from two seconds to several minutes (“skin tenting,” “doughy skin”) 7,8.
- Decreased body temperature (hypothermia) in hypovolemic shock
- Increased body temperature: 98.6-104 °F (37-40 °C) in heat exhaustion 10 and infections, such as flu or bacterial pneumonia
- Body temperature over 104 °F (40 °C) in heat stroke 9
- NOTE: Warm skin does not necessary mean fever, and cool skin does not necessary mean hypothermia.
Other possible effects:
- Capillary refill time: >4 sec 1
- Dry mucous membranes (dry mouth), dry, cracked, chapped lips, swollen tongue 27
- Very sunken and dry eyes
- Rapid, faint or impalpable pulse
- Increased frequency of breathing (hyperventilation), or respiratory depression 1
- Very increased heart rate (tachycardia): can exceed 140/min 1
- Swollen parotid glands on both sides (parotitis) 33
- Possibly impaired consciousness (somnolence, coma)
- Blood pressure: decreased; in hypovolemic shock, systolic pressure may drop under 60 mm Hg 6
Extreme Dehydration and Death
In adults, dehydration results in death after loss of 10-15% of body weight 2.
NOT Typical for Dehydration
- Cloudy urine is rather the symptom of kidney or bladder infection or inflammation or urinary stones than dehydration. Dehydration by itself usually results in dark but not cloudy urine.
Blood in Urine (Hematuria)
- Blood in urine can result from the infection, inflammation, cancer or injury of the urinary tract, but less likely from dehydration itself.
- However, some athletes sometimes have hematuria and this may be related to dehydration 22.
- Even severe dehydration by itself does not necessary cause calf/leg cramps in endurance athletes 11,12. Many doctors still believe dehydration in combination with muscle fatigue causes leg cramps or Charley horse(s) 35,36.
- Eye twitching is not a characteristic symptom of dehydration, but it can occur in accompanied disorders, such as hyponatremia or hypokalemia.
- Hands shaking (tremors) is also not typical for dehydration.
Red eyes are not typical for dehydration, but can result from an underlying cause, such as dengue fever 25.
It seems there is insufficient scientific evidence about dehydration as a cause of swollen uvula (uvulitis).
Swollen Lymph Glands (Nodes)
There is lack of evidence that dehydration would cause swelling of the lymph glands in the neck or armpits. It is possible that normal lymph glands are more palpable in dehydration due shrinking of the surrounding tissues.
Probably Not Directly Related to Dehydration:
- Bloating (can be associated with constipation due to dehydration)
- Knee pain
- Nosebleeds (dry nasal mucosa in severe dehydration may increase the risk of nosebleeds though)
- Ringing in the ears or tinnitus (can appear temporary before fainting due to severe dehydration) 32
- Yawning (except when dehydration affects sleeping)
- Emedicine (Mild, moderate and severe dehydration)
- Nature.com (Exercise performance)
- Kokopellisearcandling.com (Chronic dehydration)
- Uconn.edu (Dehydration and mood)
- Mayo Clinic (Dehydration symptoms)
- SC.gov (Dehydration)
- Nejm.org (Skin turgor)
- Emedicine (Skin turgor)
- WebMD (Heat exhaustion and stroke information)
- Childrenshospital.org (Heat stress)
- PubMed (Muscle cramps)
- PubMed (Muscle cramps)
- CDC (Cholera)
- PubMed (Migraine triggers)
- PubMed (Migraine)
- PubMed Central (Bad breath or halitosis causes)
- PubMed Central (Dehydration and psychological performance)
- PubMed (Heat exhaustion and flushed facial skin)
- PubMed (Dehydration and acute abdominal pain)
- NIH.gov (Food poisoning)
- NIH.gov (Hyperthermia)
- PubMed (Blood in urine)
- PubMed Central (Hunger and thirst)
- Travmed.com (Jet lag)
- MedlinePlus (Dengue fever)
- Allaboutvision.com (Dark circles under the eyes)
- Nasa.gov (Dehydration symptoms)
- Mayo Clinic (White tongue causes)
- Drugs.com (Acute kidney failure)
- Americanskin.org (Dry skin)
- Cancer.org (Mouth sores)
- PubMed (Vasovagal syncope and tinnitus)
- Medscape.com (Swollen parotid glands)
- Nature.com (Perception of thirst)
- Dukehealth.org (Charley horse)
- Stanford.edu (Charley horse)
- Raiterclinic.com (Prevention)
- Psc.gov (Drinking water week)