Saturday, January 13, 2024

How to diagnose diabetes in the laboratory.. Determination of fasting blood sugar. Detect sugar in urine

Diagnosing Diabetes in the Laboratory: A Multi-Step Approach

Several laboratory tests can help diagnose diabetes, each offering different insights into your blood sugar levels. Here's a breakdown of the methods you mentioned:

1. Estimating Fasting Blood Sugar (FBS):

  • This test measures your blood sugar level after an overnight fast of at least 8 hours.
  • A normal FBS level is less than 100 mg/dL (5.6 mmol/L).
  • An FBS level of 126 mg/dL (7.0 mmol/L) or higher on two separate occasions indicates diabetes.
  • A level between 100-125 mg/dL (5.6-6.9 mmol/L) is considered prediabetes, a risk factor for developing diabetes.

2. Detecting Sugar in Urine:

- Benedict's Test:

This classic test involves boiling urine with a copper-based solution. In the presence of glucose, the solution changes color, indicating a positive result. While sensitive, it's less specific and can react to other sugars and substances in the urine.

- Clinitest Tablets:

Similar to Benedict's test, these tablets change color when dipped in urine with glucose. They offer increased convenience but still lack specificity.

- Urine Glucose Test Strips:

These dipsticks are the most common method for detecting glucose in urine. They react specifically with glucose and change color, providing a quick and easy way to check for its presence.

However, it's important to note that:
  • Urine glucose tests are not definitive for diabetes. Many factors, such as pregnancy, infections, and certain medications, can cause glucose to appear in the urine.
  • A negative urine test doesn't rule out diabetes. If your blood sugar levels are very high, your kidneys may still be able to reabsorb all the glucose, leaving none in the urine.

3. Estimating Blood Sugar Levels After Glucose Intake (Oral Glucose Tolerance Test, OGTT):

  • This test measures your blood sugar levels before and after consuming a sugary drink.
  • Blood samples are typically taken fasting, one hour, and two hours after drinking the solution.
  • Specific blood sugar thresholds at each time point help diagnose diabetes or prediabetes.
  • Urine samples may also be collected during the OGTT to provide additional information.


  • FBS is the preferred initial test for diabetes diagnosis due to its simplicity and accuracy.
  • Urine glucose tests can be a helpful screening tool but should not be used for definitive diagnosis.
  • The OGTT is often used when FBS results are inconclusive or in specific situations where risk factors suggest further evaluation.

Consult your doctor:

If you have any concerns about your blood sugar levels or are experiencing symptoms of diabetes, consult your doctor for proper diagnosis and management. They will likely discuss your medical history, symptoms, and recommend the most appropriate tests based on your individual case.