Test For Presence Of Sugar In Urine: Purpose, Procedure, And Results

Introduction – Why Detect Sugar in Urine?

Detecting sugar in urine is important because it helps identify kidney related abnormalities. The presence of glucose in urine often signals diabetes or defects in renal glucose reabsorption. It also provides a quick method to assess metabolic health without requiring blood samples. Detection is typically done using dipstick strips or Benedict’s test, which change color in the presence of glucose, allowing rapid evaluation.

Objective

To carry out an experiment to test for the presence of sugar in the provided urine sample.

Theory – What Is Urine & Why Glucose May Appear?

The urine is a waste product excreted by the body, which the kidneys filter from blood. It is eliminated from the body through urination, where it comes out through the urethra. In human beings, urine is normally pale yellow and is a clear liquid consisting of water with several chemical substances added to it, including uric acid, urea, enzymes in traces, hormones, and carbohydrates.

Characteristic of Normal Urine

The characteristics of normal urine include:

Significance of Detecting Sugar in Urine

Detecting sugar in urine helps in:

Early Detection of Diabetes

Sugar detection in urine is very important because diabetes mellitus can lead to serious complications if the disease is not treated or kept under proper control. Some of the complications are damage to kidneys and nerves, cardiovascular diseases, and problems with vision.

Monitoring Diabetes

For people already suffering from diabetes, checking urine sugar regularly will indeed help them manage their diseases much better by keeping medications as well as lifestyle under control.

Renal Glycosuria Identification

Sugar in urine can also give a clue for renal glycosuria, an abnormality of the kidney where kidneys excrete glucose into the urine despite normal blood glucose concentration.

Tests for Detecting Sugar in Urine

The following are the tests that may be used to detect sugar in a urine sample.

• Benedict's Test

• Fehling's Test

• Clinitest

• Enzymatic Glucose Oxidase Test

Benedict's Test

The test takes its name from Benedict's solution, an aqueous solution of copper(II) sulfate (CuSO4) and sodium citrate. Benedict's solution is used to test for the presence of reducing sugars.

It tests for reducing sugars of a ketose moiety in the urine of a patient. The diagnostic implications of this are that the presence of glucose in neither the human urine nor the blood is normal.

Procedure

• Take a clean, dry test tube.

• Measure using the measuring cylinder, and take 2 ml of the urine sample.

• Transfer the measured urine to the test tube.

• Add 5 ml of Benedict's reagent to the urine sample in the test tube.

• Secure the test tube with a holder and place it close to the Bunsen burner.

• Heat the test tube for 2 minutes with continuous stirring.

• Observe any changes.

Observation

• A yellow precipitate after heating may appear in the test tube, and the precipitate may form slowly, indicating that there exists sugar in the urine sample.

• The sugar concentration colour determines the colour of the precipitate, where the colour may either be yellow, green, or brick red.

Fehling’s Test

Fehling's test has two solutions:

• Fehling Solution A: Copper(II) sulphate, blue aqua.

• Fehling's Solution B: An aqueous solution that is clear, colourless, and contains sodium potassium tartrate and sodium hydroxide

When heated with the urine sample, glucose reduces the copper(II) sulfate, forming copper(II) oxide as a coloured precipitate. The colour is indicative of either the presence or the concentration of glucose in the urine.

Procedure

• Obtain a clean and dry test tube.

• Two ml of the urine sample is measured using a measuring cylinder.

• Pour the measured urine into the test tube.

• Add 2 ml of Fehling's Solution A and shake well.

• Add 2 ml of Fehling's Solution B to the same test tube and then gently shake both the solutions.

• Take the test tube with a holder and hold it by heating it near the Bunsen burner for two minutes, constantly stirring it.

• Note the changes.

Observation

• On heating some green precipitate is formed in the test tube indicating that sugar is present in the sample.

• The colour of the precipitate will be yellow, green, and even brick red with the sugar concentration.

Clinitest

The Clinitest tablet, commercially available, tests for the presence of reducing sugars in urine. It has in place copper sulfate, sodium hydroxide, and other reagents that if put into a sample of urine, the reaction of the glucose with those reagents, will have a similar result as Benedict's test. It is routinely used in clinical practice due to its ease and speed of execution.

Procedure

• Take a specimen of urine in a clean test tube or container.

• Add a few drops of water to the urine specimen.

• Drop a Clinitest tablet into the sample.

• Note the reaction there will be a colour change depending on the concentration of glucose.

• Match the colour produced with a standard chart provided with the Clinitest kit.

Observation

The colour change indicates that there are reducing sugars, like glucose, in the urine. Its intensity is proportional to the concentration of sugar.

Enzymatic Glucose Oxidase Test

This is a test that is more specific compared to many of the others and quantitative in terms of measuring glucose. This test uses an enzyme that specifically reacts with glucose and forms gluconic acid and hydrogen peroxide.

The hydrogen peroxide reacts with a chromogen to produce a coloured compound. The intensity of this colour is measured spectrophotometrically, meaning that we can determine the concentration of the glucose in the urine exactly.

Procedure

• Take a sample of urine in a clean test tube.

• Add the glucose oxidase reagent to the sample.

• Let the reaction run for a specified duration.

• If you are using a spectrophotometer, then absorbance is to be measured at a max.

• Form a standard curve by comparing your results with a standard curve to give you the number of glucose in the urine.

Observation

• The urine sample tested turned into a coloured compound hence, glucose was present.

• The colour intensity will also give us glucose and the magnitude of glucose.

Sugar in Urine NEET MCQs (With Answers & Explanations)

Important questions asked in NEET from this topic are:

• Characteristics of normal urine

• Tests for detecting sugar in urine

Practice Questions for NEET

Q1. Which of the following properties of urine is not normal?

1. Slightly acidic pH

2. Yellow color due to urochrome

3. Clear appearance

4. Sweet smell due to high sugar content

Correct answer: 4) Sweet smell due to high sugar content

Explanation:

Urine is typically slightly acidic (pH 4.5-8), has a yellow colour due to the presence of urochrome, and appears clear (unless there is an underlying health condition). However, a sweet smell in urine can indicate the presence of high sugar levels, which is not normal and can be a sign of diabetes. The composition of urine includes water, urea, creatinine, and various dissolved salts and organic compounds. Its specific gravity ranges from 1.005 to 1.030, depending on hydration levels and solute concentration. Dark yellow or cloudy urine may indicate dehydration, infection, or other health issues. The presence of proteins, blood, or ketones in urine can signal underlying medical conditions requiring further evaluation.

Hence, the correct answer is option 4) Sweet smell due to high sugar content

Q2. The odour of urine is due to

1. Urochrome

2. Urinode

3. Urea

4. Melanin

Correct answer: 2) Urinode

Explanation:

Urine is a liquid waste product produced by the kidneys as they filter blood. Urinode is a volatile organic substance that is responsible for the smell of urine. Urine contains water, salt, electrolytes, and waste products like urea. Normal urine is pale straw or transparent yellow and has a mild odor.

Hence, the correct answer is option 2) Urinode.

Q3. Human urine is usually acidic because :

1. Excreted plasma proteins are acidic.

2. Potassium and sodium exchange generates acidity.

3. Hydrogen ions are actively secreted into the filtrate.

4. The sodium transporter exchanges one hydrogen ion for each sodium ion, in peritubular capillaries.

Correct answer: 3) hydrogen ions are actively secreted into the filtrate.

Explanation:

An adult human excretes, on average, 1 to 1.5 litres of urine per day. The urine formed is a light yellow-coloured watery fluid which is slightly acidic (pH-6.0) and has a characteristic odour. The pH of urine is 6.0 which is acidic due to secretion of H+ ions. H+ is proportional to 1/pH (low pH -> High H+).

Hence, the correct answer is option 3) hydrogen ions are actively secreted into the filtrate.

Also Read:

• MCQs on Characteristics of Urine

• Ultrafiltration

• Hemodialysis