There are several techniques to measure hydration status, including urine indicators like volume, color, and specific gravity. Body weight changes over short periods can also indicate dehydration levels. Chronic mild dehydration may be associated with increased risk of health issues like urinary tract infections, constipation, and hypertension. Maintaining good hydration through regular fluid intake can help reduce risks of chronic diseases.

1.
Key Tips on Hydration (Volume 4)
Hydration status and dehydration
Index
• Measuring hydration status.
• Hydration and chronic diseases.
• Signs and symptoms of dehydration.

2. MEASURING HYDRATION STATUS
KEY TIPS
ON HYDRATION For HeaLthcare Professional
distribution only
Normal hydration status
is the presumed condition
of healthy individuals who
maintain water balance1
.
Evaluation of hydration status
is not easy, as during daily
activities or exercise, fluid
compartments are constantly
fluctuating and therefore the
evaluation of a single body
fluid compartment volume is
insufficient to provide valid
information about total body
water (TBW)2
.
• Urine indicators:
Volume and colour
Specific gravity/osmolality
• Thirst
• Plasma osmolality
• Plasma sodium concentration
• Blood urea nitrogen
• Saliva specific gravity
• Bioelectrical impedance spectroscopy
• Body weight differences
Body
weight
x 0.6
70 kg
Total
body water
(TBW)
42 L
Intracellular
fluid (ICF)
28 L
Interstitial
fluid (ISF)
10.5 L
Cell membrane
Capillary wallExtracellular
fluid (ECF)
14 L
2/3
1/3
1/4 Plasma - 3.5 L
3/4
There are many hydration assessment
techniques. The following are some of the
methods used1-3
:
BODY WATER COMPARTMENTS*
* Adapted from: Elsevier, Inc. Netterimages.com. http://www.netterimages.com/images/vpv/000/000/021/21248-0550x0475.jpg
An acute change in hydration status over a period of a few hours can be assessed by:
Hydration status can be assessed by:
We will focus on some techniques that are simple, easy to perform, and inexpensive, but also
reliable, so that they can be used to evaluate hydration status during daily activities.

3. KEY TIPS ON HYDRATION
Urine indicators
Colour
Urine colour correlates quite well with hydration status as
assessed by plasma osmolality and other markers especially
when measured on the first sample of the day, but it can be
influenced by dietary factors and medications3
. Nevertheless,
it provides a useful estimate of hydration state during everyday
activities2
. The chart to the right shows that darker coloured
urine is associated with an increased likelihood of dehydration.
Volume
In a healthy adult a urine output of 1-2 litres per day may
indicate good hydration while outputs of less than about 500
mL per day can indicate deficient hydration status. An output
of more than about 300 ml per hour suggests excessive fluid
intake1
. Frequency of passing urine is a related parameter
that might also give a rough guide. Physical activity and heat
exposure can reduce urine output because of the loss of water
in sweat, while cold stress can increase it2
.
Specific gravity
Normal (euhydrated) values range from about 1,010 to 1,020 and slightly over after overnight
dehydration4
. When serious hypohydration exists, urine specific gravity may exceed 1,0305
.
Other urine indicators, including urine osmolality may also be used as indicators of hydration status6
,
but are less easy to measure.
1. EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA); Scientific Opinion on Dietary reference values for water. EFSA Journal 2010; 8(3):1459.
[48 pp.]. Available online: www.efsa.europa.eu/en/efsajournal/pub/1459.htm 2. Kolasa KM, Lackey CJ, Grandjean AC. Hydration and Health promotion.
Nutrition Today 2009;44:190-201. 3. Panel on Dietary Reference Intakes for Electrolytes and Water (2005) Dietary reference intakes for water, potassium,
sodium, chloride, and sulphate. National Academy Press: Washington DC. 4. Casa DJ, Armstrong LE, Hillman SK, Montain SJ, Reiff RV, Rich BSE,
et al. National Athletic Trainers’ Association position statement: fluid replacement for athletes. J. Athletic Training 2000;35(2):212-224. 5. Armstrong
LE. Assessing hydration status: the elusive gold standard. J Am Coll Nutr. 2007;26(5S):575SY584S. 6. Shirreffs SM, RJ Maughan. Urine osmolality and
conductivity as markers of hydration status. Med Sci Sports Ex (1998) 30: 1598-1602. 7. Farrell MJ, Egan GF, Zamarripa F, Shade R, Blair-West J, Fox P, et
al. Unique, common, and interacting cortical correlates of thirst and pain. Proc Natl Acad Sci U S A. 2006;103(7):2416–21.
The following information relates to healthy young and adult people. For healthy children and
healthy elderly people, or those with pathological conditions, the responses indicating normal
hydration (euhydration) may be different from those indicated below.
Example of how urine
colour might vary with
hydration status
Mid-brown:
Severe dehydration
Amber-orange:
Euhydration – optimally hydrated
Rich golden amber:
Hypohydration - partially dehydrated.
Probably adequately hydrated
Possibly dehydrated
Probably dehydrated
P
P
Thirst
Thirstistriggeredbybothperceptual(taste,colour,flavour,temperatureofbeverages)andphysiological
mechanisms (increases in plasma (ECF) sodium concentration and osmolarity, reductions in plasma
volume) at water deficits which correspond to a body weight loss of about 3% or more1
. Several scales
have been developed to quantify the feeling of thirst7
. Individuals can learn to recognise their own thirst
responses to various levels of dehydration.
Body weight difference measurement is a sensitive, accurate and easily
measured indicator of change in hydration status when measured regularly and under standard
conditions1
. This technique is especially appropriate for measuring dehydration that occurs over a
period of 1 to 4 hours. The base is simple: body weight loss is approximately equal to sweat loss
(corrected for the weight of fluid and food consumed and urine and faecal losses)2
. Other factors
influencing body weight should be carefully controlled. For example, carbohydrate loading in athletes
will increase body weight by retaining water with glycogen stored in muscle1
.
Note: colour reproduction may
not be accurate, do not use this
chart for diagnostic purposes.

4. HYDRATION AND CHRONIC DISEASES
KEY TIPS
ON HYDRATION FOR HEALTHCARE PROFESSIONAL
DISTRIBUTION ONLY
Dehydrationistheprocessoflosingbodywaterandcan
eventually lead to hypohydration, the condition of body
water deficit, when intake of fluids and water included
in food is insufficient to keep the body hydrated1,2
.
Hypohydration may have an effect on cognitive and
physical performance, and also on the healthstatus1-8
.
Severe hypohydration (involving a loss of more
than 10% of body weight) is a well-known cause of
mortality. However, there is increasing evidence that
mild hypohydration (involving a loss of 1-2% of body
weight)1
may also contribute to different diseases3,8
.
Low habitual fluid intake leads to chronichypohydration,
which is likely to be mild. In contrast, symptoms of acute
mild hypohydration may be severe4
.
CHRONIC MILD DEHYDRATION
Maintenance of good hydration has been shown to reduce the risk for these conditions6
.
can be present in many individuals failing to meet daily water requirements, but it has been
shown to be a common condition in some population groups, including the elderly and those
who participate in physical activity in warm environments5
.
Some studies have shown an association, although not necessarily a causal one (see different
levels of scientific evidence*), between a low habitual fluid intake and some chronic diseases3,6-8
,
such as:
• urolithiasis and cystic fibrosisIb
;
• urinary tract infections, exercise asthma, hypertonic dehydration in the infant, and
hyperglycaemia in diabetic ketoacidosisIIb
;
• constipation, hypertension, fatal coronary heart disease, venous thromboembolism,
glaucoma, and strokeIII
;
• dental diseaseIV
.
Evidence is also available, but inconsistent for bladder and colon cancer3,6
.
*Categories of evidence are as follows: Ib: Evidence from at least one randomised, controlled trial; IIb: Evidence from at least one other type of quasi-
experimental study; III: Evidence from descriptive studies, such as comparative studies, correlation studies, and case control studies; IV: Evidence from
expert committee reports, opinions or clinical experience of respected authorities, or both.

5. KEY TIPS ON HYDRATION
**See our educational materials about effects of dehydration, how to measure hydration status and water intake recommendations at:
http://www.europeanhydrationinstitute.org/educational_materials.html
1. EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA); Scientific Opinion on Dietary reference values for water. EFSA Journal 2010; 8(3):1459.
Available online: www.efsa.europa.eu/en/efsajournal/pub/1459.htm 2. Institute of Medicine: Dietary reference intakes for water, potassium, sodium,
chloride, and sulfate. Washington, DC: The National Academies Press, 2005. 3. Manz F. Hydration and disease. J Am Coll Nutr 2007;26(5):535S–541S. 4.
Maughan RJ. Hydration, morbidity, and mortality in vulnerable populations. Nutrition Reviews 2012;70(Suppl. 2):S152–S155. 5. Maughan RJ. Impact of
mild dehydration on wellness and on exercise performance. Eur J Clin Nutr 2003;57(Suppl):S19–S23. 6. Manz F, Wentz A. The importance of hydration for
the prevention of chronic diseases. Nutrition Reviews 2005;63(6):S2-S5. 7. Popkin BM, D’Anci KE, Rosenberg IH. Water, Hydration and Health. Nutr Rev
2010;68(8):439-458. 8. Brocker C, Thompson DC, Vasiliou V. The role of hyperosmotic stress in inflammation and disease. Biomol Concepts 2012;3(4):345-
364. 9. Kolasa KM, Lackey CJ, Grandjean AC. Hydration and Health promotion. Nutrition Today 2009;44:190-201. 10. Manz F, Johner SA, Wentz A, Boeing
H, Remer T. Water balance throughout the adult lifespan in a German population. Br J Nutr 2012; 107(11):1673-81.
PRACTICAL TIPS TO MAINTAIN A GOOD HYDRATION STATUS
• In healthy people, adequate hydration can usually be maintained with normal drinking behaviour
and by responding to thirst2
.
• With age, the body loses its ability to have a thirst response to fluid deficit2
. Drinking regularly
is therefore desirable to maintain good hydration2
. Common antihypertensive medications may
also affect the thirst mechanism.
• Water replacement can be enhanced by consuming beverages at meals and in other social
situations2
.
• Monitoring hydration status is recommended. Assessing urine colour provides a useful estimate
of the hydration state during everyday activities9
**.
GROUPS PARTICULARLY VULNERABLE TO DEHYDRATION:
• The elderly: Dehydration is commonly believed by geriatricians to be an acute precipitating
factor for hospital admissions, with added heat stress probably increasing symptoms4
.
• Infants and children are more susceptible to dehydration than adults. Special care has to be
given during periods of frequent vomiting or diarrhoea.
SOURCES OF WATER IN THE DIET:
• It is calculated that of the total water needed:
The adequate intake of water recommended by EFSA1
** varies with age and gender and provides
a guideline water intake. However, individual requirements will vary according to factors such as
environmental temperature and level of physical activity.
70-80%from beverages (all types,
not just plain water)1,10
.
20-30%typically comes from food and
However, this may vary greatly
depending on the diet that an
individual chooses1,10

6. Recognising signs and
symptoms of MILD dehydration
KEY TIPS
ON HYDRATION For HeaLthcare Professional
distribution only
Fluids are continuously lost from the body. Water is
lost via respiration and through the skin, renal system,
and gastrointestinal tract1
and this water needs to
be replaced. The daily water requirement depends
on a number of factors including the person’s diet,
environment, age and activity level1
. For adolescents
over 14 years old and adults the European Food Safety
Authority (EFSA) has given an adequate water intake
of 2 L for females and 2.5 L for males*2
.
Dehydration occurs when the body loses more water
than it takes in. Mild dehydration (equivalent to a
1-2%2
decrease in body mass) may have an effect on
performance and may lead to an increased risk of
adverse health outcomes3
:
Physical performance: Dehydration can adversely
affect exercise performance and it is estimated from
research that dehydration equivalent to 2% of body
mass loss is where a negative effect on endurance
performance may occur4
.
Cognitive performance: Acute dehydration - such as
that resulting from 2 hours exercising in the heat-
can indeed affect mental performance. However, in
situations where less severe dehydration occurs (such
as when refraining from drinking for a relatively short
period of time) authors have generally failed to find
evidence of cognitive impairment5
.
Disorders and Disease: There is strong evidence
for an association between chronic systematic mild
dehydration and urolithiasis, urinary tract infection,
hyperglycaemia in diabetic ketoacidosis, and mitral
valve prolapse. Association with constipation,
hypertension, coronary heart disease, stroke, venous
thromboembolism, dental disease, gallstones, and
glaucoma is less strong6
.
Is your physical performance
lower than usual?
Do you feel tired and lethargic?
Are you constipated?
These might
be signs of
mild dehydration
* Please consult our Educational material section at the address below to check water adequate intakes for other ages and special conditions.
www.europeanhydrationinstitute.org/educational_materials.html

7. KEY TIPS ON HYDRATION
SIGNS AND SYMPTOMS OF DEHYDRATION
may include:
* thirst3
* tiredness3
* palpitations due to an increase in heart rate7
* increased body temperature as a result of decreased blood flow to the skin and sweating
compromising thermoregulation7
Although these signs and symptoms are neither specific nor sensitive, it is important to
consider whether dehydration might be the cause.
70-80%from beverages
(all types, not just plain water)2,8
20-30%typically comes from food and about
Most people drink in response to thirst, and in many cases this is enough to avoid dehydration.
However, it is important to take into account that the regulatory mechanism impairs with age, and it
may not always be possible to drink when thirst arises.
Under special circumstances, when large amounts of water and electrolytes are lost due to vomiting,
diarrhoea, or even sweating (e.g. after intensive sport or during hot weather), oral rehydration salt
solutions or electrolyte solutions are needed.
In order to ensure an appropriate amount of water, it is important to take into
account that of the total water consumed, about:
However, this may vary greatly depending on the diet that an individual chooses2,8
1. Panel on Dietary Reference Intakes for Electrolytes and Water (2005) Dietary reference intakes for water, potassium, sodium, chloride, and sulphate.
National Academy Press: Washington DC. 2. EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA); Scientific Opinion on Dietary reference
values for water. EFSA Journal 2010; 8(3):1459. Available online: www.efsa.europa.eu/en/efsajournal/pub/1459.htm 3. Kolasa KM, Lackey CJ, Grandjean
AC. Hydration and Health promotion. Nutrition Today 2009;44:190-201. 4. Cheuvront SN, Carter R, Sawka M. Fluid balance and endurance exercise
performance. Curr Sports Med Rep 2003;2:202-8. 5. Szinnai G, Schachinger H, Arnaud MJ, Linder L, Keller U. Effect of water deprivation on cognitive-
motor performance in healthy men and women. Am J Physiol Regul Integr Comp Physiol 2005;289(1):R275-80. 6. Manz F, Wentz A. The importance
of good hydration for the prevention of chronic diseases. Nutr Rev. 2005;63:S2-S5. 7. Kavrouras SA, Anastasiou CA. Water physiology. Nutrition Today
2010;45:S27-S32. 8. Manz F, Johner SA, Wentz A, Boeing H, Remer T. Water balance throughout the adult lifespan in a German population. Br J Nutr
2011;1-9 [Epub ahead of print].

8.
http://www.europeanhydrationinstitute.org/