T1 Basics

Successful management of diabetes is as much about information as it is about insulin or oral medications.
 Diabetes Basics is designed to supplement the information you receive from your Diabetes Team.

Always consult your diabetes team before making any changes in your diabetes management.

What is T1 Diabetes?

Type 1 diabetes is an autoimmune disease in which the body destroys insulin-producing beta cells in the pancreas. Insulin is required by the body to use glucose, the simple sugar that most foods are broken down into by our digestive system. Without insulin, the body starves to death. It’s important to note that everyone is insulin-dependent. People without diabetes make insulin in their pancreas. People with Type 1 diabetes must inject insulin.

According to the National Institutes of Health, an estimated 850,000 to 1.7 million Americans have Type 1 diabetes. Of those, about 125,000 are kids 19 and under. An additional 30,000 Americans develop Type 1 diabetes every year, 13,000 of whom are children. Type 2 diabetes is much more prevalent, with an estimated 16 million Americans having Type 2. Millions of people with type 2 diabetes have not yet been diagnosed.


Once over 90% of the beta cells are destroyed, the body is no longer able to regulate blood sugar levels and the patient develops some or all of the classic symptoms of diabetes:

  1. Excessive thirst ( Polydipsia )
  2. Excessive urination ( Polyuria )
  3. Excessive hunger
  4. Weight loss
  5. Fatigue
  6. Blurred vision
  7. High blood sugar level
  8. Sugar and ketones in the urine
  9. Kussmaul breathing (rapid, deep, and labored breathing of people who have ketoacidosis or who are in a diabetic coma)
  10. Vaginal yeast infections in girls (even infants and toddlers)
  11. Bed wetting, especially when the child was not wetting previously
  12. Dehydration ( despite good fluid intake )
  13. Vomiting
  14. Confusion
  15. Flu-like symptoms
  16. Fruity odor to breath

While the symptoms appear abruptly,
the development of the disease actually occurs
over a much longer period of time.

If you suspect that you or your child has diabetes, contact your doctor immediately.
Untreated type 1 diabetes can lead to a very serious condition called diabetic ketoacidosis, which can be fatal.


What Causes T1?

Diabetes develops gradually. Studies performed by the Joslin Clinic1 have shown changes as much as nine years before the actual presentation of diabetes symptoms. The development of Type 1 diabetes can be broken down into five stages:

1. Genetic predisposition
2. Environmental trigger
3. Active autoimmunity
4. Progressive beta-cell destruction
5. Presentation of the symptoms of Type 1 diabetes

Type 1 Diabetes at the Islet Level

A healthy islet
Click to see a larger image.
An islet under attack
Click to see a larger image.
This graph illustrates the progression
of islet mass loss that leads to overt
type 1 diabetes.
Click to see a larger image.

According to research by Dr. David Harlan of the NIH/NIDDK, some people with long standing type 1 diabetes have measurable c-peptide production, which may help reduce their risk of complications and could indicate that the body continues to generate new islets even in the face of the autoimmune attack of type 1 diabetes.
Islet images courtesy of the Diabetes Research Institute.

People with type 1 diabetes have a genetic
pre-disposition to the disease,
but one or more environmental insults
is required to trigger disease.

People with type 1 diabetes have a genetic pre-disposition to the disease, but one or more environmental insults is required to trigger disease. This fact can be derived from studies of identical twins with Type 1 diabetes. When one twin has Type 1 diabetes, the other twin gets diabetes only half the time. If the cause of Type 1 diabetes were purely genetic, both identical
twins would always have Type 1 diabetes.

One environmental trigger is thought to be the Coxsackie B virus. Researchers at UCLA found that a small segment of GAD is structurally similar to a segment of a Coxsackie B protein. GAD is found on the surface of insulin-producing beta cells. The implication is that the body’s immune system, after warding off the Coxsackie B virus, continues to attack beta cells because of the similarity of GAD to the virus.2

The environmental trigger results in the production of autoantibodies. People with Type 1 diabetes have antibodies in their blood that indicate an “allergy to self,” or an autoimmune condition. One autoantibody found in people with Type 1 diabetes is the islet cell antibody. This antibody is often present months or years before the diabetes presents. Other antibodies include the GAD (or 64-K) antibody and the ICA 512 antibody. The presence of these antibodies is a sign that the body is attacking its own beta cells.


What Are the Risks of Developing T1 Diabetes?

The overall incidence of autoimmune or type 1A Diabetes in the U.S. and Western Europe is approximately 0.4% in Caucasian families in the first 20 years of life. The figure varies with its geographical distribution, being significantly higher in Finland and lower in Scotland. The incidence is lower in Asian, African American and Hispanic families and also appears to be increasing slowly.

In families where there is already a first degree relative with this form of diabetes, the chances of a future or so far unaffected child developing this condition is about 5%; slightly higher if the father is affected and slightly lower if it is the mother.

In individual cases the risk to a so far unaffected child can be further refined by establishing the HLA distribution on chromosome 6, with special regard to the presence of high risk and protective patterns. To date there are no certain estimates for the impact of environmental factors.



Type 1 diabetes is treated with daily injections of insulin. Oral diabetes medications are not effective.  Many patients with type 1 diabetes, after beginning insulin injections, experience a period of reduced insulin need called the honeymoon period. During the honeymoon period, the remaining beta cells continue to produce insulin. It is very important to continue insulin therapy during the honeymoon period, because even low doses of insulin appear to help prolong the duration of the honeymoon.

Treatment for type 1 diabetes includes:

1. Taking insulin
2. Carbohydrate, fat and protein counting
3. Frequent blood sugar monitoring
4. Eating healthy foods
5. Exercising regularly and maintaining a healthy weight

There are currently several tools available to help track and maintain blood sugar levels including insulin pumps, CGMs (Continuous Glucose Monitoring Systems), blood meters and some very exciting technologies on the horizon. To learn more, view the Management Tools section.

What Is Insulin?

Insulin is a hormone produced by beta cells in the pancreas. It has three important functions:

1. Insulin allow glucose to pass into cells, where it is used for energy.
2. Insulin suppresses excess production of sugar in the liver and muscles.
3. Insulin suppresses the breakdown of fat for energy.

In the absence of insulin, blood sugar levels rise because muscle and fat cells aren’t able to utilize glucose for energy. They signal the body that they’re “hungry.” The liver then releases glycogen, a form of stored glucose. This further increases the blood sugar level. When the blood sugar level reaches about 180 mg/dl, glucose begins to spill into the urine. Large amounts of water are needed to dissolve the excess sugar, resulting in excessive thirst and urination.

Without glucose for energy, the body begins to metabolize protein and fat. Fat metabolism results in the production of ketones in the liver. Ketones are excreted in the urine along with sodium bicarbonate, which results in a decrease in the pH of the blood. This condition is called acidosis. To correct the acidosis, the body begins a deep, labored respiration, called Kussmaul’s respiration. Left unchecked, a person in this situation will fall into a coma and die.



Why Does It Have to Be Injected?

Insulin must be injected because it is a protein. If it were taken orally, the body’s digestive system would break it down, rendering it useless.

Where Should I Store It?

Unopened insulin vials should be kept cool. Storing them in the refrigerator will help them last as long as possible. Never freeze insulin, however, as freezing can destroy it. Open insulin, whether vials or pens, can be kept at room temperature for about a month.

Where Does Insulin Come From?

Insulin used by people with diabetes can come from three sources: human (created via recombinant DNA methods), pork, or beef. Beef insulin has been discontinued in the US, and essentially all people who are newly diagnosed are placed on human insulin.

What Kinds of Insulins Are There?

Insulin is classified according to how long the insulin works. There are several types of insulin, listed here in order of rate of action. Be aware that duration of insulin action varies by individual, activity level and location of injection.


Types of Insulin (Trade Names) Supplier Appearance Begins Working Peak Activity All Gone
Short Acting
Novolog® / NovoRapid® ( insulin aspart ) Novo Nordisk Clear 10-15 minutes 30-60 minutes 4 hours
Apidra® (insulin glulisine ) Sanofi Aventis Clear 10-15 minutes 30-60 minutes 4 hours
Humalog® ( insulin lispro ) Eli Lilly Clear 10-15 minutes 30-60 minutes 4 hours
Regular ( Humalin, Actrapid, Velosulin® ) Eli Lilly and Novo Nordisk Clear 30 minutes 2-4 hours 4-8 hours
Intermediate Acting
NPH Eli Lilly and Novo Nordisk Cloudy 2-4 hours 6-8 hours 12-15 hours
Long Acting
Lantus® ( insulin glulisine ) (Insulatard® ) Aventis Clear 4-6 hours No Peak 24+ hours
Levemir® ( insulin determir ) Novo Nordisk Clear 1-2 hours 2-12 hours (mild, varies by dose) Up to 24 hours (varies by dose)
Pre-Mixed (Action Varies)
NPH / Regular 70/30 or 50/50 are common mixes Eli Lilly and Novo Nordisk Cloudy 30 minutes Varies 18-24 hours
NPH / Humalog 75/25 or 50/50 Eli Lilly Cloudy 10-15 minutes Varies 12-15 hours
Novalog Mix 70/30 Novo Nordisk Cloudy 10-15 minutes Varies 10-12 hours
 Adapted from Understanding Insulin-Dependent Diabetes, 11th Edition by H. Peter Chase, M.D. and drug company data.


Insulin Injections

Insulin should be injected into the subcutaneous (Sub-Q for short) tissue which lies between the muscle and the skin. When
injected here, insulin is absorbed at a steady rate. This helps you maintain good control. There is sub-q tissue all over your body,
but some places are better than others for giving insulin, because they are away from large blood vessels and nerves. The best
places for injecting insulin are:

Upper arms
The front and sides of your thighs
Abdomen (at least two inches away from the navel)

Rotation and Absorption

It’s important to change the site of your injections. Injecting in the same spot can cause lipohypertrophy, a buildup of fat under
the skin which can slow absorption.

Insulin is absorbed fastest from the abdomen, followed by the upper arms, the thighs, and the buttocks.
Because the rates of absorption vary considerably from one body region to another, the American Diabetes Association currently
recommends rotating injection sites within body regions rather than rotation to a different region with each injection.

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