Introduction
Approximately 17 million in U.S. have diabetes mellitus (7.3% of the adult population), but only half have been diagnosed. The incidence is increasing rapidly, and is expected to double by 2010. Not only is diabetes a costly condition estimated at $100 billion per year, but it is a leading risk factor in many other diseases that adversely affect pilot's career such as heart disease, stroke, vision, kidney disease, claudication, impotence and neurologic disease. Almost 800,000 Americans are diagnosed with diabetes each year and nearly 200,000 will die from the disease. It is the 7th leading cause of death in the United States. Diabetes shortens the expected lifespan of an individual by 5-10 years. Fortunately, the condition is treatable, and in most cases, pilots may be granted authorization for all classes of airman medical certification.

For an excellent, thorough discussion of type II diabetes, please see the American Family Physician Monograph on the subject.

Diabetes Mellitus- A Mixed Disease

Diabetes is not a single disease, but a mix of causes that have a common end result of blood glucose (sugar) levels elevated above normal. Two broad types of diabetes exist, Type I and Type II. Two other types of diabetes include Gestational (pregnancy-related) diabetes and diabetes due to other diseases and conditions.

Diabetes mellitus that is prone to causing comas due to severely elevated blood glucose, and which requires insulin for control, is termed Type I diabetes mellitus or immune-mediated diabetes . Formerly known as insulin requiring diabetes, it is the most life threatening form of the disease and may be diagnosed at any age. The body’s ability to produce its own insulin from the pancreas is destroyed in this condition. To survive, Type I diabetics require one or more shots of insulin daily.

Type II diabetes mellitus is much less prone to comatose states and frequently can be controlled without the use of insulin. It was previously known as non-insulin dependent diabetes mellitus (even though insulin was sometimes used for enhanced control). Oral medication (pills) and lifestyle changes in diet and exercise are usually adequate to control Type II diabetes .

Both types of diabetes mellitus are serious conditions that require careful monitoring and treatment to slow or prevent the numerous complications of each. The FAA treats the two types of diabetes mellitus quite differently because of the relative differences in range of blood sugars and possible effect on alertness and consciousness.

Basic Pathophysiology

Blood sugar is maintained as relatively constant levels in a fine balance by diet input, the body's production of insulin, its resistance to insulin and stores of carbohydrates. The normal peaks and valleys of blood sugar are dampened by the blunting effect of insulin and the enhancing effect of adrenal hormones.

With diabetes, there is an absence of the blunting effect and blood sugars may rise unchecked. In response to rising blood sugar through the dietary absorption of all foods, but sugars or carbohydrates (CHOs) in particular, the pancreas releases insulin to move CHO from the blood into the liver. In the liver, the simple CHOs are stored in a more complex form caused glycogen.

If the blood sugar drops due to missing meals or from extra consumption of sugar due to exercise, the adrenal glands above the kidneys release chemicals which trigger the release of glycogen from the liver and its conversion to glucose. This is a safety valve to prevent blood sugar from dropping too low. Low blood sugar results in impaired concentration, unconsciousness or even death. An individual feels this dropping blood glucose as anxiety, tremors, hunger, thirst, and confusion.

Certain medications, beta-blockers, will block these symptoms of hypoglycaemia and place an individual at risk for undetected hypoglycaemia. The concurrent use of these medications with diabetes mellitus adversely affects FAA certification decisions in diabetics.

Type I diabetes mellitus results from an absolute deficiency of insulin production from the pancreas. Type II diabetes mellitus may be from a relative deficiency in insulin production, the body's resistance to insulin or increased production of glycogen from the liver and its conversion to glucose. Type II diabetes mellitus is more prone to occur in overweight individuals.

Symptoms of Diabetes

Many people with diabetes do not know they have the condition. Diabetes may be discovered on a routine FAA medical examination when the urine is tested for sugar. Often, a routine blood test during a periodic health exam finds elevated levels of glucose (sugar) in the blood. Symptoms may vary widely. People may notice increased thirst, frequent urination, unexplained weight loss, fatigue or infections. Rarely, diabetes first shows itself as unconsciousness or coma. This indicates very serious disease.

Diseases of the Small Vessels

Diabetes affects the body by damaging blood vessels, in particular very small blood vessels. The result is progressive and accelerated narrowing of the vessels and impairing the function of organs. The kidneys may gradually fail and manifest the failure by high blood pressure, and the leaking of glucose and protein in the urine (checked for in all FAA Airman medical exams).

The nervous system initially manifests the damage as a loss of feeling, including temperature, touch and vibration, in the feet and hands. The circulation in the extremities is also impaired and an individual may note coolness of the feet , pale colour or non-healing ulcers. Men, especially smokers, may note impotence with impaired circulation and nerve function in the penis. Diabetes is the leading cause of blindness in the U.S., which is caused by leaking of blood from the retina in the eye.

Diseases of the Larger Vessels

Diabetics have accelerated development of diseases of the larger vessels, which can cause sudden death. Coronary heart disease is the cause of death in over 50% of Type II diabetics versus approximately 30% in non-diabetics. Strokes are 2-4 times more likely, as is heart disease, in diabetics as the non-diabetic population. Peripheral vascular disease, which causes leg cramping with exercise contributes to non-healing ulcers of the feet and may even result in amputation, is four times more likely in diabetics.

Control of blood sugar levels may substantially reduce both the small and large vessel complications of diabetes. FAA medical certification of diabetic pilots is more likely if control of diabetes mellitus is achieved before the development of any of these complications. See the American Family Physician article, Attenuating Cardiovascular Risk Factors in Patients with Type 2 Diabetes.

High Risk Groups for Diabetes Mellitus

The cause of Type I diabetes mellitus is unknown. There may be ethnic and genetic risk factors. Infectious causes have also been postulated, but not proven. Type I diabetes mellitus may declare itself at any age, often in dramatic fashion with mental confusion or coma. Type II diabetes mellitus usually presents in adulthood and often goes undetected until discovered during a routine physical examination or laboratory testing for other reasons (such as FAA periodic exams). Several non-white ethnic groups are at increased risk over whites.

Characteristics associated with Type II diabetes mellitus include obesity, increasing age, physical inactivity and women with previous diabetes in pregnancy. Smokers with diabetes have a tremendous increase in the risk of diabetic complications.

Diagnostic Criteria for Diabetes Mellitus

The American Diabetic Association and medical authorities recently revised the standards for diabetes mellitus and a "borderline" condition known as Impaired Glucose Tolerance (IGT). Three values are generally measured in diabetics.

The fasting blood sugar is a value determined after not eating or drinking anything but water for approximately 8-12 hours prior to testing. A normal value is less that 116 mg%. People with IGT have values <126 mg% but above 115 mg%, while individuals with fasting glucose values above 126 mg% confirmed with a second separate sample meet the criteria for diabetes mellitus.

The 2-hour glucose is measured 2 hours after drinking a glucose solution given as part of a glucose tolerance test. This test is not usually required to make the diagnosis of diabetes. A "casual" or "random" blood glucose is measured without a pre-test fast. Values over 200 mg% meet a criterion for diabetes mellitus. Blood sugar levels between 140-200 mg% represent IGT, while normal individuals will have levels below 140 mg%.

Impaired Fasting Glucose (IFG) is a condition that is a risk factor for later development of diabetes. People with fasting levels between 110 and 126 mg% have IFG.

A third value commonly measured is the glycosylated haemoglobin or haemoglobin A1C. This test is not a direct increase of blood sugar but gives a picture of the general range of glucose over the previous 3-4 months. A normal individual will have less than 7% of their haemoglobin with glucose molecules attached. Diabetics tend to have 7% or more of their haemoglobin with glucose molecules attached. Hgb A1C values vary significantly from laboratory to laboratory. Changes in Hgb A1C occur slowly over weeks to months and are only useful in trend analysis of diabetes management. The diagnosis of diabetes is not made by Hgb A1C levels, but elevated levels are suggestive of the diagnosis. Newer tests, such as serum frucosamine, may be more useful as a short term glucose trend analysis and a management tool.

Treatment of Diabetes

The control of blood sugar and management of diabetes is accomplished through several strategies , often used in combination. One strategy is using diet and exercise to control weight and glucose levels in Type II diabetics. Additional control is achieved through several types of medication to lower blood sugar. Type I diabetics and those Type II diabetics unable to maintain adequate control with the above strategies require the use of insulin. Insulin is given daily or more frequently by injection, as no oral form is available.

Weight Control- Diet and Exercise

Over three quarters of Type II diabetics are overweight. By restricting dietary caloric intake, many people with IGT or Type II diabetes mellitus may obtain adequate control of their weight and blood sugar. Weight loss may dramatically increase life expectancy in diabetics and increase the effectiveness of oral medication, if required. For an individual to reap the benefits of weight loss, the loss must be sustained. The American Diabetes Association has listed the food values of many types of food servings. Calories and nutrient value are listed on all manufactured food labels, frequently with ADA ratings for ease in calculation of dietary plans. A nutritionist is particularly useful in educating newly diagnosed diabetics with menu planning for weight reduction. Frequently, the ADA cookbook is used for a wide variety of recipes.

An exercise program is a valuable compliment to dietary planning for weight reduction and blood sugar control. Exercise is potentially effective in lowering blood glucose for up to half a day. The benefits of aerobic exercise may yield improvements in coronary heart disease and peripheral vascular disease. Because of the increased risk of heart disease, a diabetic should consult with their personal physician before initiating a program. Diet and exercise must be balanced, as each effects glucose levels, particularly for those on medications.

American Family Physician, January 15, 2004, has two excellent patient information handouts on diet and exercise to control diabetes. There is also an accompanying editorial on the importance of these methods in controlling diabetes. See Editorial: "Preventive Therapy for Diabetes: Lifestyle Changes and the Primary Care Physician", Patient information: "Sticking to Lifestyle Changes: Increasing Physical Activity" and Patient information: "Sticking to Lifestyle Changes: Healthy Eating".

Oral Medications for Diabetics- Pills

Type II diabetics who cannot achieve or sustain adequate blood sugar control with diet and exercise will usually benefit from oral medication. If blood sugar levels are not severely elevated, many physicians will recommend a several month trial of diet and exercise before starting medication. Five types of oral medication are currently available. Several types are waverable by the FAA after proper evaluation.

Sulfonylureas

Sulfonylurea medications were the first category of oral diabetic agents. They work by increasing the release of insulin from the pancreas and making more available to lower blood sugar. This category is more effective in recently diagnosed, older and obese individuals. They are effective in approximately 85% of people, but some individuals lose their responsiveness. The major side effect is excessive lowering of the blood sugar, hypoglycemia. This is aeromedically significant and pilots are required to show stability without hypoglycemia before obtaining medical authorization. Some commonly used sulfonylureas include glypizide (Glucotrol), chlorpropramide (Diabenase), glyburide (Glynase, Micronase, DiaBeta) and glimepiride (Amaryl).

Metformin- Glucophage

Metformin (Glucophage) was approved for use by the FDA in December 1994. It's primary advantage is that it does not increase the risk of hypoglycemia as sulfonylureas. Although equally effective in lowering blood sugar, it works by a different mechanism. Insulin levels are not affected, but the liver's release of glucose into the blood is inhibited. Metformin may also have a favourable effect on cholesterol and triglycerides. It is usually well tolerated after some initial diarrhoea and abdominal gas, but must be used with caution in those few individuals with medical conditions affecting the acid-base balance in the blood or heavy alcohol consumers. Metformin can be taken once or twice daily. A Letters to the Editor in American Family Physician points out the metformin use may be associated with vitamin B12 deficiencies and suggests monitoring and treatment strategies.

Acarbose - Precose

Acarbose (Precose) lowers peak levels of blood sugar by delaying the intestine's conversion of complex sugars into simple ones which enter the blood stream. After a meal, rather than a quick rise in blood sugar and then an insulin response (inadequate in diabetics), those taking acarbose will have a more gradual rise in blood sugar. This is analogous to a leaned out engine with a lower fuel consumption rate, though the aircraft (body) has the same fuel (food) load. It may not lower Hgb A1C as much as sulfonylureas and metformin, but may be used individually or in combination with each. The major side effects are diarrhoea, intestinal gas and abdominal pain. It must be taken before each meal to be effective.

Troglitazone-Rezulin

 - No Longer Approved or Sold

Troglitazone was one of the newest oral diabetic medications available. The FDA removed its approval of the drug and the manufacturer voluntarily recalled all medication and agreed to stop selling it on March 21, 2000. Post approval research showed Rezulin caused significant liver damage in some users. The FAA initially waived this medication in early March 1998, but no longer allows the medication to be used since it has lost FDA approval. See the article in the Federal Air Surgeon's Bulletin by Dr. Warren Silberman on the FAA's current policy on certification of pilots previously on Rezulin.

Avandia (rosiglitazone) & Actos (pioglitazone):

The newest oral antidiabetic medications and similar to Rezulin, both Avandia and Actos are now authorized.

Repaglinide - Prandin

Prandin is in another class of medications called meglitinides that lower blood sugar by stimulating release of insulin from the pancreas. This medication may be used in combination with Glucophage. It's use is approved by the FAA and can be waived after proper reporting.

Rosiglitazone - Avandia

This new class of oral medication was approved by the FDA in May 1999. Unlike other medications that increase insulin production or decrease glucose release from the liver, Avandia increases cells' sensitivity to insulin. The FAA has authorized Avandia for Special Issuance medical certification.

Pioglitazone - Actos

Like Avandia, Actos is waverable for pilots who use this medication which was approved in July 1999.

Insulin

Insulin injections are used to treat Type I diabetics who have an absolute insulin deficiency, as well as approximately 1/3 of Type II diabetics with severe (>350 mg%) elevations of blood sugar. Insulin was initially made from beef or pork sources, but now is available as genetically engineered human form. Insulin is categorized by how long it takes to act and its duration of action. Recently, insulin lispro (Humalog) was approved as a very fast acting form, allowing individuals to take insulin immediately prior to meals rather than 30-60 minutes prior. The main advantage of insulin is its tremendous ability to rapidly lower blood sugar. This is also one of its major disadvantages, as hypoglycemia and coma is possible if taken in inappropriately high doses, meals are skipped or physical activity is more than anticipated. Of course, the inconvenience of refrigeration, injections, needle disposal and careful glucose monitoring, all necessary, must be considered. For diabetics not controlled by other means, insulin may significantly prolong and improve their quality of life.

Alternative Therapies

Although not widely accepted within the medical community, some alternative treatments for diabetes have been advocated. Limited research is available. Please see an article in American Family Physician, September 1, 2000 on Alternative Therapies: Part I. Depression, Diabetes, Obesity for more information on the state of research on chromium, garlic and alpha lipoic acid for the treatment of diabetes.

Diabetic Emergencies

Diabetics need to be very familiar with how to handle diabetic emergencies primarily, hypoglycemia or low blood sugar, hyperglycemia or high blood sugar and insulin shock or coma due to ketoacidosis. Many of the restrictions and requirements imposed by the FAA on insulin requiring pilots with Special Issuance Authorizations for Third Class certification are designed to decrease the possibility of a diabetic emergency in flight.

As noted below, the FAA will grant Special issuance Third Class medical certificate to pilots who have met very stringent criteria. The FAA will not issue First and Second Class medical certificates for pilots using insulin.

Monitoring Diabetes Control

Individuals with diabetes should measure their blood sugar regularly. Some require monitoring several times a day, while others may monitor it less frequently. Generally, people using insulin require more frequent monitoring of blood glucose to determine insulin dosages and the need for snacks. Those on oral medications or controlled with diet and exercise may be able to monitor their blood sugar less frequently. Monitoring generally requires a device to obtain a small amount of blood to put on a chemical treated strip of paper/plastic. This strip is inserted in a machine which will give a reading of the blood sugar. A log of these readings should be maintained for adjustments in the treatment of diabetes.

Pilots with Diabetes – Special Issuance Medical Certificates

Pilots with diabetes controlled with diet and exercise alone are eligible for medical certification without requiring a Special Issuance Authorization. They must demonstrate adequate control of their diabetes and the absence of any complications. Regular reports from their treating physicians are required with each FAA medical application. The AME may issue a certificate if the pilot is otherwise qualified.

First and Second Class Special Issuance Authorizations

Diabetic pilots whose blood sugars are well controlled on oral medication and not using insulin may be granted a Special Issuance Authorization (SIA) for First and Second class certification after they demonstrate control and the absence of related diabetic complications.

The medical evaluation required includes a physician evaluation and physical examination. There should be no evidence of eye damage, nerve damage or significant skin ulcers due to diabetes. A physical examination will detect these conditions. Diabetic complications to the kidneys can be excluded by a urinalysis looking for protein and sugar. Neither should be present. Heart disease must be excluded by a normal result on a exercise maximal stress test.

If blood pressure is controlled with medication, no medication that would block the body’s natural symptoms of hypoglycaemia or low blood sugar may be used. This excludes using beta blockers in diabetic pilots with hypertension. However, pilots who use Prandin (repaglinide), Avandia (rosiglitazone), Glucophage (metformin) or Actos (pioglitazone) may be waived to fly when taking beta-blockers as these medications have a low risk of hypoglycaemic episodes.

Finally, the pilot must demonstrate control of the blood sugar and have no history of hypoglycaemia on FDA approved medications. Control is demonstrated by monthly Haemoglobin A1C values within 1-2 % of the laboratory’s highest normal values. Recently, representatives from the FAA Aeromedical Certification Division stated that A1C values less than 10% could be favourably considered.

The results of these tests must be reviewed by the FAA before a Special Issuance Authorization is granted. See the FAA protocol in our Information Resources section for Diabetes - Oral Medication Specifications and Diabetes - Diet Controlled.

Diabetics Treated With Insulin - Third Class Special Issuance

The FAA will certify some diabetic pilots who must use insulin for control of their condition. This authorization is limited to Third Class privileges only. Please refer to the FAA Aeromedical Certification Division specifications for complete details. . Note that pilots are encouraged to apply for their medical certificate prior to beginning or resuming any flight training. The process may take several months. As of May 1998, approximately 50 pilots requiring insulin for diabetes had been certified under this provision. You may also go to our Information Resources section to print out the FAA protocol for evaluation of insulin requiring diabetic pilots.

The pre-flight and in-flight monitoring requirements for diabetic pilots using insulin are rather complex and cumbersome. As stated above, they are designed to minimize the possibility of a diabetic emergency occurring in flight. These requirements are for in-flight only and do not reflect appropriate management on the ground. To lower the risk of insulin shock in flight, the required blood sugar values are somewhat higher in flight than those desired for optimum control when the pilot is on the ground.

Pilots are required to have a glucose monitor that they can use in flight and the appropriate supplies (not expired) to check their blood sugar at several phases of flight. They must also have several 10 gram (1/3 oz.) snacks of readily absorbable glucose available for the planned duration of the flight.

Pre-flight testing requires documentation of blood sugar levels between 100-300 mg% within 30 minutes of takeoff. If greater than 300 mg%, the pilot may not fly the flight. If less than 100 mg%, the pilot must eat a snack and confirm the level is above 100 mg% before flying.

In-flight testing is more cumbersome, particularly for the task saturated pilot. The overriding concern is the safe conduct of flight. A pilot should delay any required blood sugar testing in critical phases of flight with increased operational demands. Instead, the pilot should eat or drink a 10 gram snack and measure the glucose one hour later. If still unable to measure glucose at one hour later, the pilot should take a 20 gram snack and land at the nearest suitable airport.

The schedule for in-flight testing includes hourly checks of blood sugar (ouch!) and one check within 30 minutes of landing. If the blood sugar is below 100 mg%, the pilot should take a 20 gram snack. No snack is required if the blood sugar is between 100-300 mg%. The pilot should land at the nearest suitable airport if the blood sugar is above 300 mg% and not take off until the level can be maintained between 100-300 mg%. This is quite a bit of testing and presumably will require some practice. Conducting this testing at night may be particularly difficult. The well controlled and highly motivated pilot will be able to overcome these obstacles and maintain a Special Issuance medical certificate.

For more information on certification of insulin requiring diabetic pilots, see the Flight Safety Foundation article by Dr. Stanley Mohler on new medical standards and special issuance provisions for insulin requiring pilots, including in-flight glucose monitoring requirements. Download the FAA Protocol for Pilots with Insulin Controlled Diabetes from our Information Resources section. Also see a case report from the Federal Air Surgeon's Medical Bulletin on Diabetes Mellitus in an Airman and the personal story of the first insulin requiring pilot granted a Special Issuance, " Diabetic Pilot Flying in Style".

FAA Reporting Requirements

The completed diabetic evaluations may be mailed to the FAA at:

Federal Aviation Administration
Aeromedical Certification Division
CAMI Bldg./ AAM-300
P.O. Box 26080
Oklahoma City, OK 73126-9922

This is a very broad overview of a complex subject with many nuances. Often clinical narratives from specialists may not necessarily address all of the aeromedical issues involved. Incomplete information can result in significant delays in the certification process.