When you were diagnosed, you were probably told you had either Type 1 or Type 2 diabetes. Clear-cut and tidy. Since diabetes occurs in two types, you have to fit into one of them. Many people do fit clearly into one of these categories, but some do not. Those who clearly fit a type at diagnosis may find the clear lines begin to smudge over time. Are there really only two types? Are you really the type you were told you were? Could you even have more than one type of diabetes, and is your original diagnosis still correct after all these years?
A Short History Of Types
Described and treated since ancient times, diabetes has certain characteristics that have long been recognized. Before the discovery of insulin, people found to have sugar in their urine under the age of 20 usually died in their youth, while those diagnosed when over the age of 40 could live for many years with this condition.
Beginning in the mid 1920s, those who got diabetes when young (juvenile onset) were put on insulin, and those who got it when older (adult onset) often were not. However, the mechanisms that led to this difference in treatment were unknown. The only marker that differentiated the two types at that time was the presence in the urine of moderate or large levels of ketones when blood sugars were high. If significant ketones were present, the person could not make enough insulin, needed injected insulin to control the blood sugar, and was called insulin-dependent.
In the early 1980s a breakthrough was made in understanding childhood onset diabetes. It became clear that this early onset form was actually an autoimmune disease in which the body destroyed its own beta cells. The antibodies that the immune system put out during this attack distinguished it from adult onset diabetes. For the first time, one type of diabetes had a clear cause that made it different.
|Differences In The Three Major Types Of Diabetes|
|Type 1||Type 1.5/LADA||Type 2|
|Avg. age at start||12||35||60|
|Typical age at start||3-40*||20-70*||35-80*|
|% of all diabetes||10% (25%**)||15%||75%|
|Antibodies||ICA, IA2, GAD65, IAA||mostly GAD65||none|
|Early treatment||insulin is vital, diet & exercise changes helpful||pills or insulin vital, diet & exercise changes helpful||pills helpful, diet & increased activity essential|
|Late treatment||insulin, diet, exercise (occasionally pills)||insulin, pills, diet, exercise||insulin, pills, diet, exercise|
* may occur at any age if all antibody positive cases are included, ie Type 1 and Type 1.5
From Using Insulin © 2003
Definitions became clearer. Type 1, called IDDM (insulin-dependent diabetes mellitus), now was recognized as an autoimmune disease that appeared primarily in childhood or adolescence. Near the final phases of the attack, the person stops producing insulin and requires injected insulin. At the time of diagnosis, such a person often has excessive thirst and urination, has lost a lot of weight, and has an extremely high blood sugar. This person is normal weight or thin when Type 1 diabetes starts and may stay relatively trim through life. Type 1 occurs in about 10% of all people who have diabetes. Treatment for this type revolves around adjusting the dosages and number of insulin injections to match diet and exercise.
Type 2 or NIDDM or non-insulin-dependent diabetes mellitus, on the other hand, was described as high blood sugars occurring in a person over 40 who is overweight and sedentary and also has a family history of this type of diabetes. At the time of diagnosis, there may be no symptoms, or the person may have mild symptoms, such as blurred vision or more than normal thirst and urination. The person continues to make insulin, but the insulin production is not sufficient to keep blood sugars normal. Treatment for Type 2 diabetes revolves around varied combinations of diet, exercise, medications, and/or insulin injections.
Note that the use of insulin does not make someone "insulin-dependent" or a Type 1! Some 30 to 40% of those with Type 2 use insulin, but even when insulin is used, this type of diabetes continues to be non-insulin dependent diabetes mellitus or NIDDM, because death will not occur if insulin is discontinued. Some 90% of people with diabetes are considered to have Type 2.
In the early 1990s the definition of Type 2 was further refined to distinguish those with and without Syndrome X. Syndrome X is strongly associated with insulin resistance and with high total cholesterol (over 200), high triglycerides (also over 200), low HDL (under 40 mg/dl), high blood pressure, and gout.
Those with an apple figure, who carry excess weight predominantly in their abdomen, are at the highest risk of developing Syndrome X. The cholesterol and blood pressure problems associated with Syndrome X trigger accelerated cardiovascular disease, which can lead to heart attack, stroke, and kidney disease.
Syndrome X includes all those people who have resistance to insulin. Some 25% of Americans fall into this high risk category, although only about 30% of them will develop Type 2 diabetes at some time in their lives. Type 2 diabetes occurs when the body can no longer produce enough insulin to keep up with the increased need for insulin. People with Syndrome X also tend to develop high blood pressure because of this insulin resistance.
Not all of those typically classified as Type 2 have insulin resistance and Syndrome X, however. As evidence of this, a study of people with Type 2 was done in Bruneck, Italy, and published in October, 1998. Eighty-four percent of the people in the study had insulin resistance, while 16% did not. Are these 16% nonetheless to be called Type 2?
When "Type 2" occurs without insulin resistance, it may be referred to as Type 1.5 or Type 2-s (for insulin sensitive) or Type 2-d (for insulin deficient). Type 1.5 occurs in adults who usually are lean or normal weight. These people have normal insulin sensitivity but, like other people with Type 1, their insulin production is deficient. When their blood sugars are controlled, they usually do not have the high risk for cholesterol, blood pressure, or cardiac and vascular problems typically found in true Type 2 diabetes. This type of diabetes shares characteristics of both Type 1 and Type 2. Of all the people with diabetes, roughly 10% will have classic Type 1, 75% will have Type 2 (insulin resistant), and another 15% will have Type 1.5.
In their book, Diabetes, Type 2 and What To Do (revised October, 1998), Virginia Valentine, June Biermann and Barbara Toohey relate that in their 1993 edition of the book, they described June who developed diabetes in her sixties as a lean Type 2-d. She was similar to the many people in the 16% group in the Italian study described earlier. In 1998, they defined June as a Type 1 who got diabetes later in life. They feel this description more closely follows the American Diabetes Association revised system, as published in Diabetes Care, January 1998, in which Type 1's are insulin deficient and Type 2s are basically insulin resistant. I prefer to keep the third category, Type 1.5, which clearly defines a group that represents a sizable portion (about 16%) of those who have diabetes but are neither ketosis-prone nor insulin-resistant.
Other forms of insulin resistant diabetes also can be seen in gestational diabetes, polycystic ovary disease, acanthosis nigricans, and maturity-onset diabetes of the young or MODY. Insulin resistant diabetes can also be unmasked by medications like prednisone. In rare cases, nonresistant forms of diabetes may also be seen following trauma to the pancreas or pancreatic surgery. This last form is insulin dependent because no insulin can be produced once the pancreas is removed or severely damaged.
Most people with diabetes have Type 1, Type 1.5 or Type 2. As more is known about the causes of diabetes and more treatments are developed, more types or sub types are certain to be defined.
Why Is Knowing Your Type Important?
Properly understanding your type of diabetes lets you know whether you have been correctly diagnosed, but more importantly, it makes you aware of whether or not you are receiving correct treatment. For example, a person diagnosed with Type 1 diabetes needs insulin right away since destruction of beta cells has been going on for awhile. Not until about 90% of the beta cells are destroyed does someone typically begin to have symptoms. If the person does not clearly fit the model for Type 1, a diagnosis of Type 2 may be made and oral agents may be prescribed, even though little insulin production capability remains.
If they are lucky, these agents might stimulate the few active beta cells to produce more insulin for a short time, and the blood sugar may be controlled temporarily. However, soon an oral agent will fail, and injected insulin will be needed. If the oral agent does not work, the person will continue to be very sick until insulin is started. If Type 1 had been recognized right away through an antibody test, using insulin immediately might lead to fewer problems with control, since this often allows insulin production to continue for a longer period of time. Blood sugar control is easier when beta cells continue to work.
Knowing your diabetes type can also give you a better understanding of the changes that may occur to you as you age and your disease progresses. For example, if you have had insulin-resistant diabetes for several years and it has become harder to control on a sulfonylurea medication, you may find that your C-peptide level is now low, and insulin may now be required. If your C-peptide is normal, adding another oral agent and paying closer attention to your food and exercise choices may be all that is needed. Both situations can occur as the disease progresses and are not necessarily a result of poor practices on your part.
Dr. David Bell, a clinician and researcher in Birmingham, Alabama, wanted to see if he could take a group of people with Type 2 diabetes who were already on insulin and eliminate insulin use by substituting a combination of oral medications. He first tested C-peptide levels and chose only those who had normal levels. Of the 130 people with adequate C-peptide levels in his 1997 study, 100 were able to discontinue insulin use altogether and control their diabetes on various doses of glyburide and metformin, medications that were not available when many of the patient's insulin use was begun. Dr. Bell found that their overall control, measured by a HbA1c level, was better on these two oral medications than it had been on two doses of insulin a day. Other people in the study were able to improve their hemoglobin levels by using glyburide, metformin, and one dose of insulin at dinner or nighttime.
Researchers have determined that the Type 2 patients who are most likely to control their blood sugars on a combination of oral agents alone are those least overweight (BMI of 30 or less), with shortest duration of insulin use, and C-peptide levels normal or only slightly low.
Who Is Most Likely To Be Misdiagnosed?
Many people with Type 2 diabetes are not diagnosed at all. This rampant problem means some 8 million Americans do not know they have this disease. Symptoms are usually minimal or nonexistent, sometimes for years, and so the person is simply not treated for diabetes. An elevated blood sugar is only picked up when the person goes in for a routine physical exam or visits the doctor for another problem, like a cold or a flu.
Among people who are diagnosed with diabetes, misdiagnosis of the type happens most often when the person does not have the body type or age expected for Type 1 or Type 2. For example, a person who is 38 and slender has mildly elevated blood sugars. Is this person Type 1 or Type 2? He is older and his blood sugar may not be as high as a typical Type 1, but he is too thin for a true Type 2. Perhaps he has Type 1.5 with diminished insulin production but no insulin resistance. If the older person who is slim has very high blood sugars when diagnosed, the type more likely will be thought to be Type 1.
Or consider a child of 14 who is 40 pounds overweight and has high blood sugars. Does this child have Type 1, Type 2, or MODY (a different type of diabetes genetically predetermined)? Due to overeating, poor nutrition habits and a sedentary lifestyle, more and more children are now developing Type 2 at an early age. In fact, Dr. Gerald Bernstein, president of the American Diabetes Association, says one-fourth of new cases in people under age 20 are now Type 2. In the Journal of the AMA, November, 1998, researchers are recommending that diabetes screening be considered for sedentary, overweight people as young as 15 as a way to prevent the complications that years of high blood sugars can cause.
What about the person who is 50 years old, has high blood sugars, is 15 pounds overweight, but has a pear shaped body? Is she Type 1 or Type 2? She could be an older-than-usual Type 1 or she could be a Type 2 with a strong family background of diabetes, meaning that a modest weight gain is all that was needed for diabetes. This is especially true if body fat is high and deposited intraperitoneally (in the gut).
These cases indicate that people often do not fit into clear profiles. When the traditional profile does not match the person, understanding what may have caused the diabetes and determining how it should be treated is often problematic.
Does Your Type Ever Change?
Blurring of the lines between Type 1 and Type 2 diabetes is becoming increasingly common. Due to aging or the general progress of the disease, people with one type of diabetes tend to take on characteristics of the other. As a result, some people with diabetes may have characteristics of both types.
If Type 1's begin to exercise less and gain weight around the middle, as many people do when they age, they may become not only insulin deficient but also insulin resistant. They then can develop the cardiac risks associated with Syndrome X and require medications to lower cholesterol and blood pressure. They will require more insulin to control their blood sugars, and certain medications typically used in Type 2 diabetes, such as Glucophage, may help in their control.
On the other hand, as Type 2 diabetes progresses, especially if it is not well-controlled and the pancreas is placed under additional stress, insulin production may diminish to a point where it can no longer keep up with need. A sulfonylurea may no longer be able to stimulate the beta cells to produce enough insulin. Medications in addition to sulfonylurea, such as Precose or Prandin, may be needed. As insulin production falls further, injected insulin will be required to keep blood sugars from rising. Some people with Type 2 eventually become totally dependent on insulin and can go into ketoacidosis if insulin injections are stopped.
How Can You Know Your Type At Any Age Or Stage?
When a person does not fit into a clear profile, a diagnosis of Type 1, Type 1.5, or Type 2 is not obvious. A variety of lab tests and clinical signs help to provide the critical information needed to correctly determine which type of diabetes the person has.
- Ketones: Ketones are a byproduct produced when the body uses large amounts of fat as fuel. This occurs when carbohydrate is no longer available as fuel due to a lack of insulin. When a urine or blood test shows large amounts of ketones, that person definitely has Type 1 or insulin dependent diabetes. (One rare exception is young, black males who can have ketones at diagnosis but regain insulin production.) If insulin is injected before the ketone test is administered, the opportunity to find large amounts of ketones may have passed. The urine can easily be tested for ketones at home with Ketostix or Ketodiastix anytime the blood sugar levels are high.
- Antibodies: Type 1 diabetes is an autoimmune disease, so 80 to 90% of the time when Type 1 exists, the person is producing antibodies characteristic of Type 1, such as the islet cell antibodies and GAD 64 antibodies. The blood can be tested to see if any of these antibodies are present. If antibodies specific to Type 1 are detected, the person already has or is likely to develop Type 1 diabetes. These tests are currently used in the DPT-1 trial to test relatives of those with Type 1 diabetes and detect who will develop this disease.
- High triglyceride and low HDL: Cholesterol problems characterized by high triglycerides and low HDL are typical of insulin resistance. These markers for Syndrome X are commonly found in Type 2 diabetes. A detailed cholesterol test or lipid profile test will determine this.
- Uric Acid: The high uric acid level often found in people with gout is a component of Syndrome X. If a person has a high uric acid level and high blood sugars, he usually has insulin-resistant, Type 2 diabetes.
- C-peptide: If other tests fail to indicate the type of diabetes, a C-peptide test can reveal how much insulin the person is producing. C-peptide is half of the precursor molecule to insulin that is split off when insulin is produced by the body. If C-peptide is normal or high, Type 2 diabetes is likely. If the level is significantly low, Type 1 diabetes is likely. If the level is near normal but low, the results are inconclusive. This person may have early Type 1, Type 1.5, or long-term Type 2. When external insulin is controlling the blood sugar, the C-peptide may read low due to suppression of insulin production by the beta cells. This test should be done after insulin has been reduced or discontinued, and the blood sugar has risen to 200 mg/dl or over.
When should these tests be used, since lab tests increase health care costs, and no one wants unnecessary tests? Use them when a person who is not a clear type is diagnosed with diabetes or when treatment is not working for unclear reasons. Although these tests often do not tell everything needed for a complete understanding, they can provide more of the clarification needed to properly diagnose and treat diabetes.
In summary, our understanding of diabetes and the lab tests useful to us continues to evolve. To understand your situation as information changes, you want to ask specific questions about your diagnosis and treatment. An informed, questioning approach will increase your likelihood of receiving the best care.
Mis-Typing Is Common
Misdiagnosis or an unclear diagnosis of diabetes can lead to problems in treatment and health. Misunderstanding changes in the disease as you age can also lead to mistreatment. The lack of a way to clearly define the different types of diabetes has allowed people to be misdiagnosed, especially if clarification is based on the typical body type or age. Today we have better lab tests to differentiate Type 1 and Type 2, but they often are not done and even when they are, the diagnosis may not be definitive.
When a person does not match a typical profile, mistakes can be made in creating a treatment plan. People who have Type 1 diabetes must have injected insulin to live because they produce little or no insulin themselves. People who have Type 2 will need oral medications or insulin, depending on their lifestyle and the severity of their disease. Although they make take insulin for good control, they are not insulin dependent as is the person with Type 1.
In fact most people who use insulin are not actually insulin dependent. The number of people with Type 2 diabetes who use insulin is two or three times as large as those with true insulin dependence or Type 1. Some 30 to 40% of people with Type 2 diabetes require insulin to maintain control, but even when insulin is used, this type of diabetes continues to be non-insulin dependent diabetes mellitus or NIDDM, because death will not occur over a few days if insulin is discontinued.
Many thanks to Helen Oswalt, editor of the Scripps Whittier Keeping In Touch Newsletter, for her many helpful editing suggestions.