Test For Presence of Sugar in Urine Experiment - Aim, Procedure, and Observation
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What will You learn from the Article?
Introduction of the topic
Aim of testing Sugar in Urine
Properties of Urine
Table explaining Sugar level and its associated colour
Methods of testing
Benedict’s Test
Fehling’s Test
Key learning from the chapter
Frequently asked questions
Introduction
Among the multitude of volatile and non-volatile waste substances produced in human and animal bodies, Urine is by far the most significant by-product. Produced and excreted by means of the kidney and urethra, Urine is the primary form of excreting water-soluble wastes from our bodies.
Urine has a light-yellowish colour thanks to the presence of a pigment called urochrome. It has a pH level that varies between 4.6-8 and is a complex aqueous solution of inorganic and organic matter. Besides, normal Urine constituents such as urea, oxalic acid, and lactic acid, Sugar, and blood may also be detected in case of an abnormal condition. Thus two general tests are performed to detect the presence of glucose in the Urine, which may be an indication of diabetes mellitus.
A Urine Sugar test helps detect levels of glucose that exceed the usual levels of 160-180 mg/dl. In the event of such an anomaly, the patient is diagnosed with a condition called glucosuria.
The Aim behind testing the Urine -
The procedure of testing the Urine is called a urinalysis. The test is conducted to identify a wide range of problems -
To detect the presence or absence of Sugar/glucose in a sample of Urine.
To detect diseases related to the Kidney
To detect urinary tract infections
To detect metabolic diseases related to diabetes or any other liver diseases
The colour, quantity, odor of the Urine itself specify whether something is wrong with the person or not.
Theory
The following are the important properties of Urine:
Urine has a light-yellowish colour, imparted by urochrome.
The pH of Urine lies between 4.6-8.
Organic compounds like urea, creatinine, and uric acid are generally found in Urine.
Some inorganic compounds present in Urine are sulfates, phosphates, sodium chloride, and potassium chloride.
In abnormal conditions, there may also be a Sugar trace in Urine, in addition to proteins, ketone bodies, blood, and bile.
In case glucose is detected in blood, the patient may have a condition called diabetes mellitus.
The Following Table Helps illustrate the Urine Sugar Test Colour.
Percentage of Sugar Levels | Colour of Precipitate |
No Sugar | Blue |
0.5% to 1% | Green |
1% to 2% | Yellow |
2% and higher | Brick-red |
Methods of testing Sugar level in Urine
An Introduction
The Urine glucose test performed to detect Sugar presence in Urine can be done using the following two methods.
Benedict’s Test
Fehling’s Test
Benedict’s test employs Benedict’s solution as a reagent. It is a mixture of sodium citrate, copper sulfate pentahydrate (CuSO4.5H2O), and sodium carbonate. On the other hand, Fehling’s test employs two reagents. These are
Fehling's Solution A: An aqueous blue solution of copper sulfate.
Fehling's Solution B: An aqueous and colourless solution of sodium potassium tartrate.
When a sample of Urine is boiled with these reagents, the glucose present in the sample reduces the copper sulfate in Fehling’s solution and Benedict’s solution. This changes the colour of the solution. Depending on the levels of glucose in the solution, the colours vary from brick-red, green to yellow precipitates.
Let's learn the procedure in detail through the given explanation -
Benedict’s Test
Materials Required:
Reagent (Benedict’s Solution)
A test tube
A test tube holder
Measuring cylinders
A sample of Urine
Burner
Procedure
Take a sample of Urine with the help of a measuring cylinder (2 ml).
Pour the sample into a test tube.
Pour 5 ml of Benedict’s solution into the test tube containing the Urine sample.
Securely hold the test tube and heat it on the burner for two minutes.
Keep stirring the tube.
Conclusion and Observation
Gradually, as the sample is heated, a yellow precipitate starts to form in the test tube. This indicates the presence of Sugar or glucose in the given sample.
Fehling’s Test
Material
Fehling’s Solution A and B
A test tube
A test tube holder
A sample of Urine
Measuring cylinder
Burner
Procedure
Take a sample of Urine with the help of a measuring cylinder (2 ml).
Pour the sample into a test tube.
Pour 2 ml of Fehling’s solution A into the test tube containing the Urine sample.
Pour 2 ml of Fehling’s solution B into the test tube containing the Urine sample.
Securely hold the test tube and heat it on the burner for two minutes.
Keep stirring the tube.
Conclusion and Observation
The formation of a green precipitate indicates the presence of Sugar in the sample of Urine. Based on the concentration of glucose in the sample, the Urine Sugar test will yield different colours every time.
Key learnings from the chapter -
Urine which is yellowish in colour is the most significant by-product of human waste
Urine test is the most basic procedure recommended by every doctor to detect diseases in the human body
The appearance of Urine in itself declares certain problems to an extent
Full analysis of the problem is completed only after observing through two methods (discussed in the article).
The presence of Sugar can be detected through the presence of green precipitate.
Now you know how to do a Urine Sugar test. For more on other chemical tests and related topics, register and sign up for Vedantu’s free live Classes today. You can also download our Vedantu app for convenient access to related notes and interactive online sessions.
FAQs on Test For Presence of Sugar in Urine
1. What are the two primary chemical tests used in a laboratory to detect the presence of sugar in a urine sample?
The two main tests performed to detect reducing sugars like glucose in urine are:
- Benedict's Test: This is a common qualitative test that uses Benedict's reagent. The reagent, a complex mixture of sodium carbonate, sodium citrate, and copper(II) sulphate pentahydrate, changes colour in the presence of reducing sugars upon heating.
- Fehling's Test: This test uses two separate solutions, Fehling's A (aqueous copper(II) sulphate) and Fehling's B (aqueous sodium potassium tartrate). When mixed and heated with a urine sample containing glucose, it also produces a colour change.
2. What is the basic principle behind Benedict's test for detecting sugar?
The principle of Benedict's test is based on a redox reaction. Glucose is a reducing sugar, meaning it can donate electrons. In an alkaline medium provided by sodium carbonate, the reducing sugar reduces the blue cupric ions (Cu²⁺) from copper sulphate in Benedict's solution into red or orange cuprous ions (Cu⁺), which form an insoluble precipitate of cuprous oxide (Cu₂O). The final colour of the solution depends on the concentration of the reducing sugar present.
3. What is the step-by-step procedure to perform the test for sugar in urine using Benedict's solution?
To correctly perform Benedict's test on a urine sample, follow these steps:
- Take approximately 5 ml of Benedict's reagent in a clean, dry test tube.
- Add about 2 ml of the provided urine sample to the same test tube.
- Using a test tube holder, carefully heat the mixture over a spirit lamp or burner, bringing it to a boil for about two minutes. Ensure the mouth of the test tube is pointed away from you.
- Allow the test tube to cool down.
- Observe any change in colour. The formation of a green, yellow, orange, or brick-red precipitate indicates the presence of sugar.
4. What do the different colours in a Benedict's test result indicate about the sugar concentration?
The final colour of the solution after performing Benedict's test gives a semi-quantitative estimate of the glucose concentration in the urine sample:
- Blue (No change): Absence of sugar (0%).
- Green precipitate: Trace amounts of sugar (approx. 0.5% - 1%).
- Yellow precipitate: Low concentration of sugar (approx. 1% - 1.5%).
- Orange precipitate: Moderate concentration of sugar (approx. 1.5% - 2%).
- Brick-red precipitate: High concentration of sugar (over 2%).
5. What is the medical term for the presence of sugar in urine, and what health condition does it primarily indicate?
The medical term for the presence of a significant amount of sugar (glucose) in the urine is glucosuria or glycosuria. While trace amounts can sometimes appear temporarily, persistent glucosuria is a classic sign of Diabetes Mellitus. This happens when blood glucose levels are so high (hyperglycemia) that the kidneys cannot reabsorb all the glucose from the filtrate, causing it to be excreted in the urine.
6. Why is a blood glucose test generally preferred over a urine test for diagnosing and monitoring diabetes?
A blood glucose test is more reliable and preferred over a urine test for several reasons:
- Real-time Data: Blood tests measure the exact amount of glucose currently in the bloodstream, providing immediate and accurate data.
- Renal Threshold: Sugar only appears in the urine after the blood glucose level exceeds a certain point, known as the renal threshold (typically around 180 mg/dL). A person can have high blood sugar (hyperglycemia) without it being high enough to cause glucosuria.
- Sensitivity: Urine tests can miss moderately high blood sugar levels and cannot detect low blood sugar (hypoglycemia), which is critical for managing diabetes treatment.
Therefore, while a urine test can suggest a problem, a blood test is essential for accurate diagnosis and management.
7. Besides diabetes, can the presence of sugar in urine be caused by other factors?
Yes, while diabetes mellitus is the most common cause, glucosuria is not exclusively linked to it. Other potential causes include:
- Renal Glucosuria: A rare condition where the kidneys excrete glucose into the urine even with normal or low blood sugar levels, due to a defect in the renal tubules.
- High Sugar Intake: Consuming an extremely large amount of carbohydrates or sugar in a short period can temporarily raise blood sugar above the renal threshold.
- Pregnancy: Gestational glucosuria can occur in pregnant women due to hormonal changes and increased blood flow to the kidneys.
- Certain Medications: Some drugs can affect glucose metabolism and lead to its presence in urine.
8. What are the essential safety precautions to follow while performing a urine sugar test in a science lab?
When conducting a urine sugar test, especially one involving heating, students must adhere to the following safety precautions:
- Always wear safety goggles to protect your eyes from chemical splashes.
- Handle the urine sample with care, preferably wearing disposable gloves.
- Use a test tube holder to hold the test tube while heating; never hold it with bare hands.
- Always point the mouth of the test tube away from yourself and others during heating to prevent injury from bumping or splattering.
- Handle Benedict's reagent and other chemicals with care, avoiding contact with skin and eyes.
- Wash hands thoroughly after the experiment is complete.
