What is Cystic Fibrosis-Related Diabetes (CFRD)?

Cystic fibrosis-related diabetes (CFRD) is a complication of cystic fibrosis (CF). CF is a genetic disorder that causes sticky mucus in your body. It affects many organs and body systems, including the pancreas.

If your pancreas is too damaged, it can struggle to produce enough of the hormone insulin to get sugar out of your blood. If this happens, you will develop diabetes.

This article will discuss the symptoms of CFRD, how to diagnose and treat it, and how CFRD affects people with cystic fibrosis.

How CFRD has grown

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene cause CF. This gene produces a protein that helps the mucus around your organs and tissues stay thin and move freely around your body. It also helps your lungs, digestive system, and pancreas function properly. This mutation causes the mucus to become sticky. CFRD is one of the major complications of CF due to damage to the pancreas by this mucus.

The American Diabetes Association (ADA) classifies CFRD as type 3c diabetes mellitus (T3cDM). This type of diabetes is caused by disease of the pancreas. The symptoms, diagnosis, and management of T3cDM are different from type 1 diabetes (your body produces little insulin) and type 2 diabetes (the insulin your body produces does not work properly).

Symptoms of CFRD

CFRD usually has no symptoms at first. Hyperglycemia (high blood sugar) may occur during lung infection or treatment corticosteroids. Other symptoms of diabetes, such as excessive thirst and increased urination, may be confused with CF symptoms.

Other signs to look out for include:

  • feeling more tired than usual
  • weight loss or inability to maintain weight
  • In children, stunted growth or delayed puberty
  • More lung deterioration (sudden onset)
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Diagnosing CFRD

Because CFRD is often asymptomatic, routine screening will aid in early diagnosis. The ADA and the Cystic Fibrosis Foundation recommend a 2-hour, 75-gram oral glucose tolerance test (OGTT) to diagnose CFRD. CF patients 10 years of age and older should be screened annually.

The criteria for diagnosing diabetes vary in people with CF. Blood sugar levels considered prediabetic in the general population may be considered normal in CF patients.

If your CF is stable, the diagnostic criteria for CFRD include:

  • Two-hour OGTT blood glucose of 200 milligrams per deciliter (mg/dL) or higher
  • Fasting blood sugar (measured after a night of no food) of 126 mg/dL or higher
  • A1C (blood test used to diagnose diabetes and prediabetes) of 6.5% or more
  • Standard symptoms of diabetes (excessive urination or thirst) with a blood sugar level of 200 mg/dL or higher

Diagnostic criteria for CFRD during a CF episode or corticosteroid treatment include:

  • Fasting blood glucose ≥ 126 mg/dL
  • Two-hour postprandial blood glucose level of 200 mg/dL or above for more than 48 hours

Tube feeding precautions

A patient with CF fed by tube feeding can be diagnosed with CFRD if blood glucose rises above 200 mg/dL halfway through the feeding or after two consecutive feedings.

CFRD treatment

Oral diabetes medications are not currently recommended for patients with CFRD. Insulin therapy is the most effective treatment. This will include taking rapid-acting insulin before meals. For patients with hyperglycemia between meals, a combination of fast-acting and slow-acting basal insulins can be used.

If you have CFRD, current guidelines for blood sugar level goals include:

  • Fasting blood sugar between 70 and 130 mg/dL
  • Less than 180 mg/dL two hours after a meal

With CFRD, the disease may cause temporary insulin resistance. You will need higher doses to control your blood sugar until your condition improves.


CFRD is a lifelong disease with no cure. CF patients with diabetes are more likely to have poor lung function and eventually lung failure. However, the treatment of CF and CFRD has greatly improved in recent years. People with CF are now living longer than ever before.

Cystic Fibrosis (CF): Life Expectancy

But CFRD can be successfully managed with insulin therapy, especially when diagnosed early. Annual diabetes screening for CF patients is recommended, resulting in greatly improved health outcomes.


Cystic fibrosis-related diabetes (CFRD) is a complication of cystic fibrosis (CF). CF is caused by a genetic mutation that makes the body’s normally thin mucus thick and sticky. This mutation can damage organ systems, especially the lungs and pancreas. CFRD occurs when the pancreas does not produce enough insulin to remove sugar from the blood.

For people with CF, the guidelines for diagnosing diabetes differ slightly from those for type 1 or type 2 diabetes. A condition of hyperglycemia may not lead to a diagnosis of CFRD. Annual screening of CF patients is recommended. Symptoms are about the same as when someone has type 1 or type 2 diabetes. However, you may not experience any symptoms at all.

CFRD is managed with insulin therapy. Health outcomes have improved significantly as annual screening is recommended. Early diagnosis to reduce the risk of lung failure is important.

VigorTip words

A CFRD diagnosis can feel overwhelming. You face the challenge of managing two chronic diseases at the same time. But the good news is that medical research makes it possible to successfully manage CFRD. Insulin therapy has been shown to control blood sugar in patients with CFRD.

For the best chance of success, follow the treatment plan your healthcare provider has laid out for you. This means taking prescribed medications as directed, eating a healthy diet, and exercising regularly. Be sure to consult your healthcare provider if you have any questions or concerns.

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Frequently Asked Questions

  • How common is cystic fibrosis-related diabetes (CFRD)?

    2% of children with CF have CFRD. This increases to 20% in adolescents and 40%–50% in adults.

  • Is there a difference between CFRD and diabetes?

    Although CFRD and type 1 and 2 diabetes can cause high blood sugar, the reasons are slightly different. In types 1 and 2, the cause is autoimmunity (when your immune system attacks healthy cells). With CRFD, the genetic mutation creates a harsh environment in the body that can lead to damage to the pancreas.

  • What other complications do people with CFRD have?

    People with CFRD are at higher risk for malnutrition, impaired lung function, and recurrent lung infections.