Table 1 Characteristics of methods for assessing hydration

Stable isotope dilution

N/A

Expensive and time consuming

5

5

5

5

5

Neutron activation analysis

N/A

Expensive and time consuming

5

5

5

5

5

Haematocrit

< 2% change

Influenced by many confounding factors

3

3

3

3

2

Plasma/serum osmolality

< 296 mmol/kg

Expensive and invasive

4

4

4

4

2

Serum sodium concentration

< 145 mEq/L

Expensive and invasive

3

4

4

4

2

Hormonal variables

N/A

Expensive and undetermined validity/reliability

2

4

4

5

4

Urine specific gravity

< 1.020 SG

Many confounding factors

2

2

2

2

1

Urine osmolality

< 700 mmol/kg

Many confounding factors

2

3

2

3

2

Urine colour

< 4

Many confounding factors

1

1

2

1

1

Saliva osmolality

< 61 mmol/kg

Questionable reliability

1

3

2

3

2

Tear osmolality

< 310 mmol/kg

Undetermined validity/reliability

3

3

2

3

2

Body mass

< 2% change

Many confounding factors and only works within limited time periods

4

1

1

1

1

Bioimpedance

N/A

Many confounding factors and questionable reliability

3

2

1

1

1

Vital signs^a

N/A

Questionably validity/reliability

1

1

1

2

1

Sensation of thirst

< 3 (scale of 1–9)

Low sensitivity

1

1

1

1

1