Test For Presence Of Sugar In Urine

Aim

To perform a test detecting the presence of sugar in the given sample of urine.

Theory

Urine is an excretory liquid waste, produced by a pair of a kidney, which needs to be eliminated from our body. Through the process of urination, urine is excreted from the urethra. In humans, urine is a pale yellowish liquid containing water and several other chemical components such as uric acid, urea, traces of enzymes, hormones, and carbohydrates.

Properties Of Urine

• It has a characteristic pale yellow colour.
• The yellow colour is imparted by the yellow pigment known as urochrome.
• The urine pH ranges from 4.6 to 8.
• More than 95% of urine constitutes water.
• Organic substances of nitrogenous origins found in urine are creatine, uric acid, urea.
• Other organic matter in urine are lactic acid, oxalic acid.
• Inorganic constituents are potassium chloride, sodium chloride, phosphates, and sulphates.
• Urine abnormally can contain other constituents such as ketone bodies, sugar(glucose), protein, bile and blood.
• Glucose is usually not found in urine. It appears when in blood, the glucose levels exceed the renal threshold of glucose i.e., 160 to 180 mg/dl.
• When glucose is present in urine it is termed as glucosuria. It indicates diabetes mellitus.

Also Read: Diabetes mellitus.

Sugar presence in a sample of urine can be detected by performing the following two tests:

1. Benedict’s test
2. Fehling’s test

What is Benedict’s Test?

A Benedict’s solution serves as a reagent in this test. The reagent is a blend of copper, sodium citrate and sodium carbonate and copper II sulphate pentahydrate (CuSO₄.5H₂O)

What is Fehling’s test?

In this test, the two different types of  Fehling’s solution are used:

1. Fehling’s solution – A: Aqueous solution of copper II sulphate – Blue colour solution.
2. Fehling’s solution – B: Aqueous solution of sodium potassium tartrate – Clear and Colourless solution.

When the urine sample is boiled with the two different reagents, the CuSO₄ found in Benedict’s and Fehling’s solution is reduced by the reducing agent, glucose for the formation of a coloured cuprous oxide precipitate. Depending on the glucose concentration, a yellow, green and brick-red formation of precipitates of oxides take place.

The table below depicts the colour sequence on the basis of glucose level concentration.

1. Benedict’s Test

Material Required

• Burner.
• Test tube.
• Urine sample.
• Test tube holder.
• Benedict’s solution.
• Measuring cylinders.

Procedure

• Take a clean and dried test tube.
• Using the measuring cylinder, accurately measure 2ml of the given urine sample.
• Pour the measured urine sample into the test tube.
• Add accurately 5ml of Benedict’s reagent into the test tube containing the urine sample.
• Now fix the test tube holder, bring the test tube near the bunsen burner and allow it to heat for 2 minutes.
• While it is heating, keep stirring the tube continuously.
• Observe the changes.

Observation And Conclusion

Upon heating the sample, gradually, a yellow precipitate is formed in the test tube, which indicates the presence of sugar in the given urine sample. Different precipitates are formed depending upon the sugar concentration in urine, which can be yellow, green, or brick red.

2. Fehling’s Test

Material Required

• Burner.
• Test tube.
• Urine sample.
• Test tube holder.
• Measuring cylinder.
• Fehling’s solution A.
• Fehling’s solution B.

Procedure

• Take a clean and dried test tube.
• Using the measuring cylinder, accurately measure 2ml of the given urine sample.
• Pour the measured urine sample into the test tube.
• Add accurately 2ml of Fehling’s solution A into the tube containing urine sample and shake well.
• Add accurately 2ml of Fehling’s solution B into the same test tube and mix all the solution slowly.
• Now fix the test tube holder, bring the test tube near the bunsen burner and allow it to heat for 2 minutes.
• While it is heating, keep stirring the tube continuously
• Notice the changes

Observation And Conclusion

Upon heating the sample, gradually, a green precipitate is formed in the test tube, which indicates the presence of sugar in the given urine sample.  Different precipitates are formed depending upon the sugar concentration in urine which can be yellow, green, brick red.

For more information on urine, properties of urine, different test used to check the presence of sugar in urine and other related biological concepts and experiments, visit us @ BYJU’S Biology.

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