What does it measure?
This measurement compares urine density with water. Dissolved waste products and other substances make urine denser. It helps your clinician understand fluid balance and the kidneys’ ability to concentrate urine, especially when read with blood tests and symptoms.
Before the test
- Sample
- A urine sample; the report may use a strip or a laboratory measurement.
- Preparation
- Follow any fluid instructions given for this test. Mention recent imaging contrast and medicines.
What can the result mean?
A higher result usually means more concentrated urine; a lower result means more dilute urine. Either can be an expected response to fluid intake. Persistent unusual results may lead to questions about kidney function or the hormones controlling water balance. [1]
When is it useful, and how is it read?
For thirst, unusually frequent urination, or a fluid-balance concern, interpret this alongside fluid intake, urine volume, blood glucose, and kidney function. One dilute sample after drinking water does not show a loss of kidney concentrating ability. [1]
What can affect it?
Glucose, protein, some medicines, and recent imaging contrast can affect the reading. A morning sample and one taken after drinking a lot of water are not directly comparable. [1]
Concentration can change the rest of the report
The same amount of a substance can look more concentrated in a smaller volume of urine. Specific gravity gives useful background when reading several urine findings together. [1]
Questions you might have
Does a high result only mean dehydration?
No. Glucose and other substances in urine can also raise specific gravity. [1]
Can a dipstick give the exact concentration?
It gives an estimate. A laboratory method or urine osmolality may answer a more specific question. [1]
What comes next?
Follow the collection instructions and drink as you normally would unless advised otherwise. If the result is unexpected, your clinician may compare it with urine osmolality, blood sodium, or a repeat sample. [1]
Does this result fit my fluid intake, or do we need a more specific concentration test?
The reference interval and units on your report are part of understanding your result. Understand units, reference intervals, and treatment targets.
Sources & references
Medical references & original research
Books we consulted
References that informed our explanations of the test and its context.
- Pagana KD, Pagana TJ, Pagana TN. Mosby’s Diagnostic and Laboratory Test Reference. 14th ed. Elsevier; 2019.
Practical-section sources accessed: .
For general health education. Interpreting your result and deciding on tests or treatment requires your health context and a qualified clinician.
