Diabetes – Diagnosis, Symptoms and Treatment

Doctor Nathan LeDeaux, MD

Medically reviewed by Dr. Nathan LeDeaux, MD

Medical Professional

Updated - December 22, 2020

Nathan LeDeaux is an emergency medicine physician at the University of Wisconsin and got his M.D. from Northwestern University in Chicago Illinois.

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What is Type 1 Diabetes?

Type 1 diabetes is a medical condition characterized by autoimmune destruction of beta islets cells in the pancreas, resulting in impaired insulin production and hyperglycemia.  Patients often present for the first time to the emergency department with diabetic ketoacidosis – this potentially fatal condition is characterized by metabolic acidosis, severe dehydration, and respiratory distress.  If left untreated, patients will typically die.

Type 1 diabetes is very difficult to control and typically requires the help of an Endocrinologist.  Chronically poorly controlled diabetes is a leading cause of heart, kidney, and eye disease.

What is Type 2 Diabetes?

Type 2 Diabetes is a disorder characterized by abnormally high blood sugar levels usually caused by insensitivity to insulin.  Insulin production is increased in type 2 diabetics, but the body cannot use this insulin effectively or there is not enough due to the number of cells and the amount of glucose.  The condition is far more common in individuals with a family history of diabetes or a perosnal history of obesity.  It is a leading risk factor for the development of heart disease, stroke, and peripheral vascular disease.  It is also a leading cause of kidney disease, blindness, and death in the United States.

What Causes Type 1 Diabetes?

Type 1 diabetes is caused by autoimmune destruction of the pancreatic islets that produce insulin and sense blood sugar levels. Insulin is a hormone responsible for glucose metabolism and homeostasis.  Insulin helps drive glucose into cells for energy use and promotes the synthesis of glycogen in the liver, a form of glucose that allows it to be stored for later.  When insulin insufficiency produced, serum glucose levels remain elevated – long-term elevations in glucose lead to most of the complications of diabetes.

When glucose levels are significantly elevated, the kidneys’ ability to keep glucose out of the urine is overwhelmed. This glucose in the urine pulls water and sodium out of the body. The end result of this process is severe dehydration as glucose, sodium, and water get dumped in the urinary tract and excreted out of the body through urine.

In type 1 diabetes, the body is in a state of starvation.  Serum glucose levels are elevated, but glucose has trouble entering cells and cannot be used to create the energy cells need to function. The body begins turning fat (triglycerides) into an alternative form of fuel known as ketones in order to generate energy.  Ketones are acidic compounds that acidify the blood, the extreme amounts of ketones made in type 1 diabetes can lead to extreme acidosis. This acidosis may lead to respiratory failure and cardiovascular instability.

What Causes Type 2 Diabetes?

Type 2 diabetes is caused by insensitivity to insulin.  In other words – there is no problem with insulin production, the problem is that tissues cannot properly use insulin to drive glucose into the cells.  Diabetes is frequently associated with obesity, high cholesterol, elevated blood pressure (hypertension), kidney failure, heart disease, and stroke.

Long-term elevations in blood sugar lead to tissue injury and inflammation.  This is especially problematic in the arteries, where it promotes the formation of fatty plaques.  Arterial plaques lead to reduced blood supply to tissues and organs such as the heart, kidneys, eyes, and nervous system.

The most common risk factors for diabetes include:

  • Obesity
  • Family history
  • Alcohol use
  • Sedentary lifestyle
  • Poor diet

Other conditions such as low thyroid function (hypothyroidism), Cushing syndrome, and certain medications (e.g. corticosteroids, beta-blockers) can also cause elevated blood sugars, sometimes even after they are stopped which would lead to a diagnosis of type 2 diabetes.

How Common is Type 1 Diabetes?

Type 1 diabetes is relatively common, approximately 1.6 million people in the United States have type 1 diabetes. Type 1 diabetes generally develops early in life, 75% of type one diabetes diagnoses are made below the age of 18. It is still possible to acquire type 1 diabetes later in life it is far less common, most new diagnoses of diabetes in adults is type 2 diabetes.

How Common is Type 2 Diabetes?

Type 2 diabetes is far more common than type 1 diabetes, it is estimated that 34 million people in the United States have type 2 diabetes. Unlike type 1 diabetes this condition can be diagnosed in any age but is far more common in the elderly. Individuals with obesity and low levels of physical activity are much more likely to be diagnosed with type 2 diabetes.

Signs and Symptoms of Type 1 Diabetes

The signs and symptoms of type 1 diabetes come on slowly and then rapidly escalate. General fatigue and malaise are the first symptoms and over the course of days to weeks more specific symptoms that suggest diabetes develop. The most common signs and symptoms of diabetes are:

  • Excessive thirst & drinking – polydipsia
  • Frequent urination - polyuria
  • Increased appetite & food intake - polyphagia

The excessive hunger and appetite are a consequence of the fact that the body is in a state of starvation – even though glucose levels are elevated, the body cannot use it for energy.  Frequent urination occurs because of excessive spillage of glucose, sodium, and water into the urinary tract.  This also is the cause of increased thirst and desire to drink.  As opposed to type 2 diabetes, patients with type 1 diabetes are frequently thin or skinny – type 2 diabetics are generally overweight or obese.

Patients with diabetic ketoacidosis, a complication that may develop after several days or weeks,  are typically very ill and often present acutely with:

  • Confusion
  • Respiratory distress
  • Abdominal pain
  • Nausea & vomiting
  • Severe dehydration

Diabetic ketoacidosis is the most common in newly diagnosed diabetics, the majority of people with the symptoms of type 1 diabetes have mild symptoms until ketoacidosis develops. Ketoacidosis may also be provoked by other medical conditions such as incorrect use of insulin, poor diet, infections, surgery, and the use of certain medications such as steroids.  If left untreated, diabetic ketoacidosis will lead to death.

Long-term complications of type 1 diabetes include:

  • Cardiovascular disease – myocardial infarction (heart attack), coronary artery disease, heart failure, peripheral vascular disease
  • Foot ulcers and infection
  • Neurologic disease – stroke, peripheral neuropathy
  • Renal disease – chronic kidney disease, diabetic nephropathy
  • Gastrointestinal disease – gastroparesis, fatty liver disease
  • Eye disease – retinopathy, glaucoma, blindness
  • Death

Signs and Symptoms of Type 2 Diabetes

The signs and symptoms of type 2 diabetes are largely identical to type 1 diabetes. The difference is that it presents more slowly and is diagnosed during routine doctor's visits. An elevated blood glucose is commonly the only sign of type 2 diabetes. If unrecognized and untreated the classic signs and symptoms of diabetes develop:

  • Eating excessively (polyphagia)
  • Excessive thirst (polydipsia)
  • Frequent urination (polyuria)

Diabetic ketoacidosis is also much rarer in type 2 diabetics, the complications of poor or absent treatment develop more slowly in most type 2 diabetics. These conditions are largely identical to the ones seen in poorly treated type 1 diabetes.

  • Eye disease leading to blindness(retinopathy)
  • Kidney failure – results in high blood pressure and swelling in the legs
  • Heart attack – chest & difficulty breathing – although heart attacks in diabetes may be “silent”
  • Nerve damage in the feet & hands (peripheral neuropathy) causes burning pain

Type 1 Diabetes Diagnosis

The diagnosis of type 1 diabetes is suggested based on symptoms and physical examination but typically confirmed with laboratory studies.  The diagnostic guidelines for type 1 diabetes are similar to that of type 2 diabetes and based on fasting glucose, random glucose, and hemoglobin A1C levels:

  • Fasting plasma glucose ≥126 mg/dL on 2 occasions
  • Plasma glucose ≥200 mg/dL with hyperglycemia symptoms
  • Positive oral glucose tolerance test - plasma glucose ≥200 mg/dL 2 hours after a standard glucose load
  • Hemoglobin A1C ≥6.5%

Besides serum glucose and hemoglobin A1C levels, other commonly ordered blood tests include a CMP (comprehensive metabolic panel), CBC (complete blood cell count), thyroid function (TSH, free T4), and cholesterol levels.  Your doctor will also typically perform a urinalysis and check a urine microalbumin level which is a marker of kidney damage.  If you have hypertension or symptoms of heart disease, your doctor may obtain a chest x-ray, ECG (electrocardiogram), and ultrasound of the heart (echocardiogram).

Type 2 Diabetes Diagnosis

Type 2 Diabetes is primarily diagnosed based on blood tests evaluating your glucose levels and hemoglobin A1C.  Hemoglobin A1C gives your doctor an idea of how well your diabetes has been controlled in the past several months.  The diagnosis of diabetes is made when your fasting glucose is >126 mg/dL, random blood glucose is >200, or if your hemoglobin A1C is >6.5%.

Your doctor will also likely order blood tests such as a CMP (comprehensive metabolic panel), CBC (complete blood cell count), cholesterol levels, urine microalbumin, and urinalysis.

If they suspect that you have heart disease they will likely obtain an ECG (electrocardiogram), and an ultrasound of the heart (echocardiogram).

Type 1 Diabetes Medication

Type 1 diabetes must be treated with insulin. generally, this is done under the supervision of an endocrinologist, a doctor that specializes in diseases of the endocrine system. Adjustments to the diet to minimize the amount of carbohydrates eaten are also required. 

For patients with type 1 diabetes, the goal of insulin therapy is to provide insulin in a similar manner to the pancreas natural release of insulin. This is done by giving a long-acting insulin that works throughout the day, known as “basal” insulin, and pre-meal doses of short-acting insulin, known as “bolus” insulin.  There are a variety of multiple daily injection regimens and the choice of basal and pre-meal bolus insulin depends upon patient preference, lifestyle, and cost. It is possible to give insulin continuously throughout the day using an insulin pump. In this case, only short-acting insulin is used as basal insulin is given in small doses every few minutes by the pump.

Examples of long-acting insulin and diabetes medication include:

Examples of intermediate-acting insulin include:

  • NPH (insulin isophane)

Examples of short and rapid-acting insulin include:

Blood glucose monitoring with a glucose meter is generally performed 4-7 times daily – usually before meals, mid-morning, mid-afternoon, and before bedtime.  Continuous glucose monitoring devices are available that monitor blood glucose levels in real time.

For adults with type 1 diabetes, the goal is typically to achieve an A1C value of <7%.

Type 2 Diabetes Medication

The treatment of type 2 diabetes is much more complicated than type 1 diabetes. While insulin is required with type 1 diabetes, in type 2 diabetes its use is rarer as there are a number of oral medications that can enhance the action of insulin that is already being produced by the pancreas. A healthy diet and regular exercise also play a major role in treating type 2 diabetes, as they both lower blood glucose in the short and long term. 

Patients with diabetes should get a minimum of 30 minutes of exercise a day. Walking at a brisk pace is sufficient to see reductions in glucose and improvements in other areas of health. The diabetic diet is focused on reducing the amount of carbohydrates consumed. Specifically from processed foods such as candy, baked goods, fried foods, chips, and ice cream. 

The most commonly prescribed drugs for type 2 diabetes include:

Metformin is almost always the first medication started in anyone with type 2 diabetes. This medication is well tolerated in nearly all patients and is associated with reduction in body weight. If this medication alone is not enough to lower glucose to an acceptable range other medications on this list will be started.

Patients with severe disease may also require the use of insulin. This is usually started if three medications are insufficient to control blood sugars. Patients may initially start with oral medications but require insulin at a later date if their diabetes progresses. 

Your doctor may start you on low-dose aspirin depending on your age and presence of other cardiovascular risk factors.  Patients with diabetes are also usually treated with cholesterol-lowering medications (eg, Lipitor - atorvastatin) and blood pressure reducing therapies (e.g.,Zestril - lisinopril, Cozaar – losartan). As these have been proven to reduce the risk of death from heart disease and kidney disease. 


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The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.