Diabetes Mellitus: Overview of Lab Diagnosis in Kenya



Diabetes Mellitus (DM) is a chronic metabolic disorder that affects the body’s ability to regulate blood glucose levels. The core pathophysiology is the lack of adequate insulin or response to the insulin. Laboratory diagnosis of DM is crucial for early detection and effective management of the disease. In Kenya, the diagnosis of diabetes is based on the The World Health Organization (WHO) criteria.

The diagnostic criteria for DM based on fasting plasma glucose (FPG) and 2-hour post-load plasma glucose (2hPG) are as follows:

  • Fasting plasma glucose (FPG) ≥7.0 mmol/L (126 mg/dL)
  • 2-hour post-load plasma glucose (2hPG) ≥11.1 mmol/L (200 mg/dL) during an oral glucose tolerance test (OGTT)

It is important to note that the diagnostic criteria for DM should be confirmed by repeating the test on a different day.

The OGTT is an important diagnostic tool for DM. The test involves the administration of a glucose solution to a fasting individual, followed by measurements of plasma glucose levels at 30 minutes, 1 hour, and 2 hours. The OGTT is useful in detecting impaired glucose tolerance (IGT) and impaired fasting glucose (IFG), which are pre-diabetic conditions that increase the risk of developing DM.

Role of HBA1c

Glycated Hemoglobin (HbA1c) is another laboratory test used in the diagnosis of DM. HbA1c is a measure of the average blood glucose level over the past 2-3 months. The test is useful in monitoring long-term glycemic control in patients with DM. The WHO recommends an HbA1c threshold of ≥6.5% (48 mmol/mol) for the diagnosis of DM.

It is important to note that the HbA1c test should not be used in certain populations, such as pregnant women, individuals with hemoglobinopathies, or those with renal or hepatic dysfunction.

Impaired Glucose Tolerance

Impaired glucose tolerance (IGT) is a pre-diabetic state in which the blood glucose level is higher than normal, but not high enough to be diagnosed as diabetes mellitus (DM). The diagnostic criteria for IGT are based on the measurement of blood glucose levels during an oral glucose tolerance test (OGTT).

The diagnostic criteria for IGT based on OGTT are as follows:

  • 2-hour post-load plasma glucose (2hPG) ≥7.8 mmol/L (140 mg/dL) and <11.1 mmol/L (200 mg/dL)

It is important to note that the OGTT should be performed after an overnight fast and the individual should not be consuming any food or drinks during the test.

Individuals with IGT have an increased risk of developing DM, cardiovascular disease, and other complications. The risk of progression to DM varies depending on individual factors such as age, family history, lifestyle, and comorbidities.

Studies have shown that the risk of progression to DM is higher in individuals with IGT compared to those with normal glucose tolerance. The risk of progression is estimated to be approximately 5-10% per year, and up to 70% over the course of 10 years. However, lifestyle interventions such as diet and exercise have been shown to reduce the risk of progression to DM by up to 58%

Type 1 Diabetes Mellitus

The diagnosis of type 1 diabetes (T1D) is primarily based on clinical presentation, presence of autoantibodies, and laboratory values. In addition to tests used to diagnose diabetes in general (such as fasting plasma glucose and HbA1c), there are additional tests that can be useful for the diagnosis of T1D. These include:

1. Autoantibody tests:

The presence of certain autoantibodies is a hallmark of T1D. The most commonly measured autoantibodies in clinical practice are islet cell antibodies (ICA), glutamic acid decarboxylase antibodies (GADA), insulinoma-associated antigen 2 antibodies (IA-2A), and zinc transporter 8 antibodies (ZnT8A). The presence of one or more of these autoantibodies can support the diagnosis of T1D.

2. C-peptide level:

C-peptide is a byproduct of insulin production and is secreted in equimolar amounts with insulin. In T1D, there is a deficiency of insulin production, leading to low levels of C-peptide. Measuring C-peptide levels can help distinguish T1D from other forms of diabetes, such as type 2 diabetes, in which there is typically higher C-peptide levels.

3. Genetic testing:

Although T1D is not typically caused by a single gene mutation, certain genetic variants have been associated with an increased risk of developing the disease. Testing for these genetic variants may be helpful in certain cases, such as when the diagnosis is uncertain or when a family history of T1D is present.

It is important to note that the diagnosis of T1D is based on a combination of clinical and laboratory findings, and no single test can definitively diagnose the disease. Clinical judgment and careful evaluation of the patient’s history, symptoms, and laboratory results are essential for making an accurate diagnosis of T1D.

Gestational diabetes mellitus (GDM)

This is a type of diabetes that is first diagnosed during pregnancy. GDM is diagnosed using different criteria than those used for non-pregnant individuals. The diagnostic criteria for GDM have been revised by several organizations over the years, but currently, the most commonly used criteria are those recommended by the International Association of Diabetes and Pregnancy Study Groups (IADPSG) and endorsed by the World Health Organization (WHO).

The diagnostic criteria for GDM according to the IADPSG/WHO are as follows:

  1. Fasting plasma glucose (FPG) level of 5.1 mmol/L (92 mg/dL) or higher
  2. 1-hour plasma glucose level of 10.0 mmol/L (180 mg/dL) or higher after a 75-g oral glucose load
  3. 2-hour plasma glucose level of 8.5 mmol/L (153 mg/dL) or higher after a 75-g oral glucose load

The diagnosis of GDM requires at least one of the above values to be met or exceeded. The diagnostic test should be performed between 24 and 28 weeks of gestation, or earlier in high-risk individuals.

It is important to note that GDM is associated with an increased risk of adverse pregnancy outcomes, including preeclampsia, cesarean delivery, and neonatal hypoglycemia. Therefore, early detection and management of GDM are crucial for ensuring the best possible outcomes for both the mother and the baby


Here is a table summarizing the diagnostic criteria for impaired glucose tolerance (IGT)Gestational Diabetes Melitus (GDM) and diabetes mellitus (DM) based on the World Health Organization (WHO) guidelines.


Fasting Plasma Glucose (FPG)

1 hr Post-load Glucose (75mg)

2-hour Post-Load Plasma Glucose (2hPG)



<6.1 mmol/L (<110 mg/dL)


<7.8 mmol/L (<140 mg/dL)



<7.0 mmol/L (<126 mg/dL)


≥7.8 mmol/L (≥140 mg/dL) and <11.1 mmol/L (<200 mg/dL)



≥7.0 mmol/L (≥126 mg/dL)


≥11.1 mmol/L (≥200 mg/dL)




≥5.1 mmol/L (92 mg/dL)

≥10.0 mmol/L (180 mg/dL

≥8.5 mmol/L (153 mg/dL)



As a parting shot, remember to always chart your or loved ones blood sugars. Here’s a handy 1-month log that can help you. (click here)

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