This document discusses urine analysis to detect reducing sugars using Benedict's test. Benedict's test involves adding urine to a blue copper sulfate solution. In the presence of reducing sugars like glucose, the cupric ion is reduced to a colored cuprous oxide precipitate. The color change can indicate the approximate concentration of reducing sugars, ranging from green (trace) to brick red (>2 g/dL glucose). Reducing sugars in urine, known as glycosuria, can be caused by conditions like diabetes mellitus. The document reviews the principle, procedure, interpretation and limitations of Benedict's test for qualitative and semi-quantitative detection of reducing sugars in urine samples.

1. Urine Analysis: Sugars
Dr. Salman Ansari
Dept. of Pathology
Kanachur Institute of Medical Sciences

2. Contents
● Intro
● Test
● Principle
● Procedure
● Interpretation
● Viva

3. Reducing sugar
Called “reducing” because it has a free ketone or
aldehyde group which can be donated
Examples of reducing sugar:
- Glucose
- fructose

4. Reason to test?
- Presence of detectable amount reducing sugar in urine -
called “glycosuria”
- Presence of detectable amount of glucose in urine -
called “glucosuria”

5. Causes of glucosuria:
- Type 2 Diabetes Mellitus
- Pregnancy : Gestational diabetes mellitus(GDM)
- Severe burns
- IV corticosteroids
- Severe sepsis

6. Test for reducing sugar
Benedict’s test:
- Test to detect reducing sugars in urine
- It is a qualitative test and also semi-quantitative test
- Benedict’s reagent contains:
- Copper sulphate
- Sodium carbonate
- Sodium citrate

7. Principle
● Urine is added to blue coloured copper sulphate
solution.
● Cupric ion is reduced by glucose to cuprous oxide and
a coloured precipitate is formed.

8. ● Take 5 ml of Benedict’s qualitative reagent in a test
tube.
● Add 8 drops (or 0.5 ml) of urine.
● Heat to boiling for 2 minutes
● Look for colour change
Procedure

10. Interpretation
No change of blue colour = Negative
Greenish colour = Traces (< 0.5 g/dl)
Green/cloudy green ppt = + (0.5-1 g/dl)
Yellow ppt = ++ (1-1.5 g/dl)
Orange ppt = +++ (1.5-2 g/dl)
Brick red ppt = ++++ (> 2 g/dl)

12. Report:
The given sample contains: reducing sugar
Principle Observation Interpretation
0.5 ml of urine boiled
in 5 ml of Benedict’s
reagent.
Blue colour copper
sulphate is reduced in
the presence of
reducing sugar,
leading to colour
change
Orange colour seen Reducing sugar
present

13. Viva questions
Q: What does Benedict’s test detect?
Q: What does Benedict’s reagent contain?
Q: What is the principle and procedure of Benedict’s
test?
Q: What are the advantages of Benedict’s test?
- Simple, can be performed quickly
- Cheap
- It is both qualitative and quantitative

14. Q: What are the limitations of Benedict’s test?
- False positive due to drugs like penicillin, isoniazid,
streptomycin, salicylate
- Exact concentration cannot be measured, only
rough estimate

15. References:
● Harsh Mohan - Practical Pathology - 5th edition
Questions:
salman.s.ansari92@gmail.com
For PPT, scan: