Diabetes 101: Your Complete Guide

Mayte WaliLast Updated Jan 28, 2021 11:12:23 AM ET
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Diabetes mellitus, also commonly known as diabetes, is a health condition that develops when your body becomes unable to process sugar normally. It leads to higher-than-normal blood glucose levels, meaning that glucose, which is a type of sugar, builds up in your blood. If left untreated, the high blood sugar levels associated with diabetes can damage your organs and other body systems.

Diabetes also has a hormonal component. When you eat, your stomach and small intestine absorb glucose from the food and release the sugar into your bloodstream. Insulin, a hormone your pancreas produces, stimulates other cells to take the glucose from your blood and use it for energy. Typically, your cells absorb that sugar and process it efficiently, lowering your blood sugar in the process. When you have diabetes, your body doesn’t make or use insulin properly. Your cells may also have trouble absorbing glucose, depending on the type of diabetes you have. This causes your blood sugar levels to rise, which is known as hyperglycemia.

There are two main types of diabetes: Type 1 and Type 2. Type 1 diabetes is caused mostly by genetics and is due to a functional breakdown of the cells that produce insulin. Often, Type 1 diabetes results in your pancreas producing little or no insulin. Type 2 diabetes has strong links to obesity and typically results from a combination of diet, lifestyle and genetic factors.

Type 2 diabetes is typically diagnosed at an older age, most commonly over the age of 45, whereas Type 1 diabetes is usually diagnosed in childhood or adolescence. Altering your diet and lifestyle can sometimes prevent Type 2 diabetes, but Type 1 cannot be prevented. Symptoms of all types of diabetes are similar. Additionally, leaving all types of diabetes untreated can lead to serious health complications.

According to the American Diabetes Association, in 2018, 34.2 million Americans, which is about 10.5% of the population, had diabetes. Of those 34.2 million, nearly 1.6 million had Type 1 diabetes. Additionally, about 1.5 million people in the United States are diagnosed with diabetes every year — and 7.3 million don’t even know they have it.

These numbers highlight how common this health condition is in the United States, and they also highlight its seriousness. It’s important to learn more about recognizing, preventing and treating diabetes — doing so can empower you to take charge of your health, provide support to a loved one and stay informed about vital public health issues. This guide will equip you with the foundational knowledge you need to better understand a variety of aspects related to Type 1 and Type 2 diabetes.

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Symptoms of Diabetes

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The symptoms of diabetes you might experience can vary based on how high your blood sugar levels are. Depending on the type of diabetes you have and how advanced it is, you might not experience any symptoms initially. Early symptoms of diabetes are a direct result of having too much sugar in your blood and include:

  • Frequent urination
  • Increased thirst
  • Increased fluid intake


Other symptoms may occur as a result of your body’s increasing inability to use glucose from the food you eat. These include:

  • Feelings of irritability
  • Fatigue
  • Weakness
  • Unexpected weight loss
  • Feelings of hunger
  • Nausea


Additional symptoms can occur as a result of complications of diabetes. These may also develop if you have diabetes that’s undiagnosed:

  • Blurred vision
  • Skin infections, in particular fungal groin infections (thrush)
  • Slow healing of wounds
  • Numbness and/or tingling of the hands or feet
  • Sexual difficulties such as erectile dysfunction


Warning signs of diabetes can be subtle. These may include:

  • Waking up during the night feeling very thirsty
  • Waking up to pass urine more than once per night
  • Falling asleep during the day
  • Not noticing minor injuries on your hands or feet
  • Not being able to feel hot or cold temperatures with your fingers
  • Color changes in your feet
  • Having difficulties with sexual arousal


People with Type 1 diabetes might also develop a condition called diabetic ketoacidosis (DKA). DKA happens when your body has too little insulin to allow sugar to enter your cells. Your body compensates by extracting energy from other places, such as your fat and muscle tissue. This process creates byproducts called ketones. These byproducts are acidic and alter the chemical balance of your blood, which can make you very ill.

Symptoms of DKA, in addition to the above, include:

  • Breathlessness
  • Extreme fatigue
  • Abdominal pain
  • Nausea and vomiting
  • Confusion
  • Loss of consciousness
  • Seizures


Causes of Diabetes

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Researchers believe Type 1 diabetes is primarily genetic, but there’s no single gene that determines whether you’ll develop Type 1 diabetes or not. However, several genes have been identified for their potential to increase a person’s risk of developing the condition. There’s also likely an environmental influence, but researchers don’t yet understand exactly what role it may play in whether someone develops this condition or not. Type 1 diabetes is more common in certain areas of the world and in urban areas over rural areas. There may also be an association between the development of Type 1 diabetes and the types of bacteria and viruses someone was exposed to in their early childhood.

Like Type 1 diabetes, there’s also not one exact cause of Type 2 diabetes. However, there are several risk factors that can increase your likelihood of developing Type 2 diabetes. Genetics play a role; you’re more likely to develop this type of diabetes if you have a parent or sibling with the condition.

Advancing age, obesity, lack of exercise, smoking and an unhealthy diet are well-established risk factors that can increase your chances of developing Type 2 diabetes. Diet and weight in particular play an important role. People whose diets are high in dairy products, carbohydrates and red meat are at a greater risk of developing Type 2 diabetes than those whose diets consist mainly of fruits, vegetables, white meat and whole grains.

Obesity is the strongest risk factor for Type 2 diabetes, and this is especially true when extra weight is distributed around your waistline. The scientific community believes this is because fat cells may send chemical signals throughout your body to tell other cells not to respond to insulin. This process can result in insulin resistance — your cells’ growing inability to respond to the insulin-initiated process of using glucose from your blood.

Other medical conditions associated with an increased incidence of Type 2 diabetes include high blood pressure (hypertension), high cholesterol and heart disease. If you’ve been diagnosed with any of these conditions, it’s important to get tested for diabetes as well.

Diabetes Prevention

Because lifestyle factors have such a prominent role in whether a person develops Type 2 diabetes, it’s possible to prevent the development of this condition entirely by maintaining a healthy lifestyle. Staying at a healthy weight, eating a balanced diet and maintaining a regular exercise routine are most important, along with not smoking. In terms of exercise, you should aim to get least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity activity each week to lower your risk of developing Type 2 diabetes.

Type 1 diabetes is not preventable. However, you can prevent complications by keeping your blood sugar well controlled through the management and use of insulin medication. This might involve planning out your meals carefully, remembering to take insulin at the correct time and regularly checking your blood glucose levels.

Diagnosing Diabetes

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All types of diabetes are diagnosed with blood tests. Usually, a healthcare professional takes a sample of your blood while you’re in a fasting state, meaning you haven’t eaten anything for a set number of hours beforehand. When you’ve been fasting, your blood sugar should be at a low level between 70mg/dl and 99mg/dl. Milligrams per deciliter, or mg/dl, measures the concentration of glucose in your blood. An elevated fasting blood sugar level may indicate diabetes.

If your doctor sees indications you might have diabetes, you may also undergo a glucose tolerance test. This measures your blood glucose levels before and after you consume a snack that contains a known amount of glucose to determine how your body processes the sugar. To obtain a more long-term indication of your blood sugar over time, your doctor might also perform a hemoglobin A1C test. The results of this test show your average blood glucose levels over several months, and a reading of 5.7% or less is considered normal for someone without diabetes.

Because Type 2 diabetes is common, clinicians often offer screening tests to people who are at risk of developing diabetes, including people who are overweight, people who have high blood pressure or those who are over age 45. It’s also important for doctors to screen anyone who has symptoms of diabetes — in particular young people who may have Type 1 diabetes.

As part of the screening process, your doctor might ask you about any symptoms of diabetes you’re experiencing, about any family members who might have diabetes and about your dietary and exercise habits. Although it can feel uncomfortable, it’s important to be honest with your clinician when they’re taking your history. This helps them best assess your health and determine a treatment plan tailored to your needs.

You might also undergo a physical examination, which includes checking your weight and blood pressure. If you’re already experiencing diabetes symptoms, your doctor may assess you for issues involving your eyesight and sensation in your feet. You might be asked to provide a urine sample to check for the presence of glucose, protein and ketones, which could indicate diabetes or a kidney condition.

It’s likely that, as part of your overall health assessment, your doctor will also want to check your cholesterol and other biological markers. The doctor might also start you on medications, depending on the results of your tests or as a preventative step. These are all measures to reduce your overall risk of illness.

Type 1 Diabetes, Type 2 Diabetes and Prediabetes

Type 2 diabetes is much more common than Type 1, with between 90% and 95% of people with diabetes having this form. As mentioned, Type 2 diabetes develops when your body becomes unable to use insulin normally and sugar remains in your blood. In Type 1 diabetes, which affects only 5–10% of people with diabetes, your body does not produce enough insulin to adequately take sugar from your blood and use it for energy.

Type 1 Diabetes

In Type 1 diabetes, your immune system destroys the cells in your pancreas that make insulin, and those pancreatic cells eventually lose their ability to produce insulin at all. Without adequate insulin, your body can’t use the sugar it absorbs from the food you eat. Instead, the sugar stays in your blood. The underlying reason a person develops Type 1 diabetes is thought to be due to genetic factors, and there’s no way to prevent this condition from developing.

Type 1 diabetes is a lifelong condition that’s often diagnosed when a person is a child or adolescent, which is why you may hear people refer to it as "juvenile diabetes." However, it can develop at any age. Symptoms often come on rapidly over a period of weeks or months, and they most commonly include weight loss, weakness, thirst and frequent urination. People with undiagnosed Type 1 diabetes can become very ill due to DKA, which occurs as their bodies continually try to make energy from sources other than sugar.

There’s no cure for Type 1 diabetes, but it can be managed with insulin therapy and careful dietary controls to prevent complications from occurring.

Type 2 Diabetes

In contrast to Type 1, Type 2 diabetes typically doesn’t arise due to issues with your pancreas or insulin production. Instead, it develops because of changes in your body’s cells and their response to insulin. With Type 2 diabetes, your fat, liver, muscle and other cells begin to ignore insulin signals, even though the hormone is plentiful and circulating in your bloodstream. Over time, your pancreas produces more and more insulin, and your body’s cells respond less and less. This process is called insulin resistance. As a result, sugar accumulates in your bloodstream.

Type 2 diabetes occurs mainly as a result of dietary and lifestyle factors, including poor diet, obesity and inactivity. However there are also genetic links, and people with a family history of Type 2 diabetes are more likely to develop it themselves.

Unlike Type 1 diabetes, Type 2 diabetes occurs gradually and often worsens over a period of months or years. Symptoms are usually less noticeable, and people with Type 2 diabetes are unlikely to become profoundly sick suddenly due to the condition.

Type 2 diabetes is usually managed with a combination of medication and lifestyle changes. These changes include achieving a healthy weight, changing your diet to reduce the proportion of carbohydrates and sugars consumed, and incorporating regular exercise. Unlike Type 1 diabetes, Type 2 diabetes can go into remission with effective management. People with Type 2 diabetes have been able to achieve consistently normal blood sugar readings without medication after they’ve made intensive lifestyle changes.

Prediabetes

Prediabetes develops when your blood sugar is elevated above normal levels but isn’t high enough to be considered Type 2 diabetes yet. A doctor can diagnose it when there’s evidence your body’s ability to process glucose is impaired — but not to the point for it to be termed diabetes. Prediabetes management largely focuses on making lifestyle modifications and working hard to prevent the progression to Type 2 diabetes.

Treatments for Diabetes

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If you’re diagnosed with diabetes, the types of treatments you’ll use to manage the condition will depend on whether you have Type 1 or Type 2 diabetes. Your doctor will work with you to determine what might work best for your individual health status and what’s manageable for you based on your lifestyle. With that in mind, there are several common treatments that are likely to play a role in the ways you manage life with diabetes.

Type 1 Diabetes Treatments

Several medications are available for treating Type 1 diabetes. The mainstay of treatment for people with this type is insulin medication because their bodies physically cannot produce the hormone. There are several types of insulin, and they differ in their:

  • Time of onset (the length of time it takes for the insulin to have an effect)
  • Peak time of action (when the insulin is having its maximal effect)
  • Duration of action (the length of time the insulin continues working)


Insulin is measured in "units" and is usually administered using a pen-like device that you insert directly into your skin. Some people use wearable insulin pumps, which can automatically administer the correct amount of insulin, depending on the blood sugar readings these devices obtain.

The following are some important points about insulin to keep in mind:

  • Long-acting insulins don’t have a particular "peak" and instead deliver a constant dose of insulin for an extended period of time (typically 20–24 hours). People usually take doses of these once or twice a day so their bodies always have enough insulin available to manage typical sugar-energy demands.
  • Intermediate-acting insulins work within two to four hours. They peak at between four and 12 hours and continue working for up to 18 hours.
  • Short-acting insulins work within 30 minutes. They peak within two or three hours and continue working for between 12 and 18 hours.
  • Rapid-acting insulins work right away — within a few minutes of dosing. They peak within an hour and continue to work for between two and four hours. People often take them at mealtimes and vary their doses according to the amount of sugar in the meals they’re eating. This gives their bodies an amount of insulin tailored to handle the food they’re eating without leaving too much or too little insulin in their bloodstreams.


Insulin regimens can vary widely depending on individual needs. If you have Type 1 diabetes and are using insulin, it’s important to consult with your healthcare provider regularly about making sure your insulin regimen is optimized. A typical regimen involves injections of a long-acting insulin twice a day, along with additional rapid- or short-acting insulin shots at mealtimes.

Healthcare professionals often teach people with Type 1 diabetes to count or estimate the amount of sugar in their meals and snacks. They use this information to administer the right amount of insulin either before or with that meal. This helps enable their bodies to use glucose properly.

Type 2 Diabetes Treatments

If lifestyle modifications like diet and exercise changes alone aren’t enough to keep Type 2 diabetes under control, patients often start drug therapy. These therapies involve taking medications that help their bodies respond to insulin in a more typical way or reduce hyperglycemia. Common Type 2 diabetes medications include the following:

  • Biguanides, such as Metformin, help reduce the amount of glucose your liver produces. They also help your body better respond to insulin and absorb the sugars you eat more effectively.
  • Dipeptidyl peptidase-4 (DPP-4) inhibitors, such as Alogliptin and Saxagliptin, help your pancreas produce more insulin.
  • Sulphonylureas, such as Gliclazide, stimulate your pancreas to produce more insulin.
  • Thiazolidinediones, such as Pioglitazone, reduce insulin resistance in fat cells.
  • Glucagon-like peptide-1 (GLP-1) receptor agonists, such as Exenatide and Liraglutide, improve insulin secretion from your pancreas.
  • Sodium-glucose transporter (SGLT) 2 inhibitors help your kidneys eliminate excess glucose.


People with Type 2 diabetes sometimes also need insulin therapy.

Type 2 diabetes can cause health complications that affect other systems and organs in your body. It can also increase your risk of developing other health conditions. Because of this, your doctor might have you start taking other medications that aren’t specifically formulated to treat diabetes but that lower your risk of developing other conditions. These include:

  • Statins for high cholesterol levels
  • Antihypertensive drugs for high blood pressure levels
  • Aspirin if you have a high risk of developing heart disease


Treatment for Diabetes: Adjusting Your Diet

What you eat plays a large role in both the prevention and control of diabetes. If you have diabetes, it’s recommended that you adopt a low-fat diet and avoid partially hydrogenated fats completely. Vegetable oils, nuts and seeds are ideal diabetes-friendly replacements for meat and dairy products that are high in fat. It’s also advisable to eat lean meats, such as chicken and turkey, instead of red meat when possible. Your doctor may also ask you to adopt a low-sugar diet and to swap simple and refined carbohydrates (such as candy, pastries and white bread) for complex carbohydrates such as whole grains and legumes.

Treatment for Diabetes: Monitoring Your Levels

When you’ve been diagnosed with diabetes, your doctor might ask for you to return for testing periodically so they can monitor how well your lifestyle changes and medications are working at controlling your blood glucose levels. They might also have you monitor your blood sugar throughout the day yourself, especially before and after meals. You’ll use a glucose monitor device to do this. These test kits can analyze glucose levels based on a sample of blood obtained from a tiny finger prick.

Your doctor will likely also monitor your hemoglobin A1C level, as this gives a good long-term idea of whether your blood glucose is dropping. The higher your A1C level is, the greater your risk is of developing complications of diabetes. A normal A1C level is less than 5.7%. A level between 5.7% and 6.5% indicates prediabetes, and a level of over 6.5% is in the diabetic range.

Depending on the management strategy your doctor has recommended, you might also start a weight-management program. You’ll likely require additional blood tests if your doctor has started you on certain medications.

Treatment for Diabetes: Complications Without Treatment

If you’ve been diagnosed with diabetes and don’t take steps to manage your symptoms or control your blood sugar, you put yourself at risk of developing complications.

Hypoglycemia: Diabetes is characterized by high blood sugar levels. Sometimes, treatments that aim to lower blood glucose levels can actually lead to low blood sugar. Low blood sugar can make you feel very ill, with symptoms of weakness, trembling, palpitations, abdominal pain, nausea and vomiting. In some cases, low blood sugar can result in a loss of consciousness, seizures and even death. If you’re taking any medications that lower your blood glucose levels, it’s important to be aware of these symptoms and to be able to check your own blood glucose.

Eye damage: Damage to the eyes (called diabetic retinopathy) is the most common complication of diabetes. Having persistently high blood sugar levels can damage the tiny blood vessels in your eyes. You might not notice any symptoms in the early stages, but, if it goes untreated, diabetic retinopathy can lead to vision loss and even complete blindness. People with diabetes are advised to visit an ophthalmologist regularly and to report any changes in vision right away.

Kidney damage: Diabetic kidney disease also occurs due to damage of the blood vessels within the kidneys. This leads to a progressive decline in kidney function. Kidney disease often has no symptoms until it advances to later stages. Your doctor may recommend screening tests, such as a urine test, to assess any signs of damage. If left untreated, kidney disease can lead to kidney failure. High blood pressure also contributes to kidney damage, so it’s important to keep your blood pressure within the normal range for your age if you’re diabetic.

Nerve damage: Diabetic nerve damage (called neuropathy) can develop if your blood sugar levels remain uncontrolled. This condition usually manifests in your hands and feet (where your peripheral nerves are) first. It may cause symptoms such as tingling or numbness of the extremities. Diabetes can also damage the nerves in the genitals, leading to sexual difficulties such as erectile dysfunction.

Cardiovascular disease: High blood sugar causes damage to the blood vessels in your body, particularly those in your heart. This means people with diabetes have an elevated risk of developing heart disease and related conditions such as angina and heart attacks. If you experience symptoms such as chest pain, seek emergency treatment right away.

Infections: Diabetes is a risk factor for developing frequent infections, particularly skin infections and small wounds. People whose blood sugar levels remain uncontrolled are often prone to developing fungal infections, which may manifest as an itchy rash in sweaty areas such as the groin, under the breasts or in skin folds. These infections are easily treated with a topical antifungal cream, but it’s important to report them to your doctor as soon as you notice symptoms.

Mouth: People with diabetes are also prone to developing mouth infections and gum disease. It’s essential to brush your teeth twice per day and have regular dental cleanings and checkups.

Feet: The combination of loss of normal sensation due to diabetic neuropathy and poor circulation in the feet means that you might not be able to feel pain signals from small injuries, blisters or ulcers. Keep an eye on your feet, and address any sores or blisters right away. It might be worth seeing a specialist called a diabetic podiatrist if you’re experiencing problems with your feet due to diabetes. In severe cases of foot neglect, widespread infection can occur. If the infection has progressed far enough, it may be necessary to amputate the affected foot.

Your Next Steps for Living With Diabetes

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Receiving a diabetes diagnosis will impact your life, but it’s reassuring to know that treatments and lifestyle modifications can help you manage this condition effectively. Your doctor will likely advise you to make changes to your diet, lose weight and get more active if possible. Or, you might start taking a new medication to manage your symptoms.

It’s important to remember that diabetes is a very treatable condition, and you can prevent complications by following your treatment plan. Your doctor can also help you access resources to find out more about living with diabetes. They may even be able to assist you in connecting with support groups and communities of people with diabetes.

Although it might not seem this way at first, a diabetes diagnosis can often be the ideal opportunity to make healthier life choices. When you turn these choices into habits, you might not only reduce your risk of complications from diabetes, but also reduce your risk of other conditions such as heart disease and cancers. Making these changes can improve your overall quality of life and help you manage your health successfully.

Medical content reviewed by Dr. Samantha Miller, MBChB

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