What you need to know about diabetes

Do you have type 2 diabetes, or are you at risk for diabetes? Do you worry about your blood sugar? Do you have type 1 diabetes or care for someone who does? Then you’ve come to the right place.

This page will give you an overview of what you need to know about diabetes. It will also link you to more information and, importantly, to practical guides that will help you learn what to do about having diabetes.

Many people with diabetes or prediabetes have improved their health with dietary changes. You can too! This may mean that you can reduce or eliminate diabetes medication, and these same dietary changes may help you lose weight as well.

1. What is diabetes?

A diagnosis of diabetes means that you have too much sugar in your blood. This is a problem because the sugar molecule in your blood, called glucose, can damage blood vessels when there is too much of it. Over time, this situation can harm the body in many ways and may cause serious complications.

Our guide, “What you need to know about blood sugar”, can help you learn more about both high and low blood sugar, along with other information. This guide to diabetes focuses specifically on the high blood sugar levels that occur in diabetes.

The reason that a person develops high blood sugar depends on what type of diabetes that person has. However, all types of diabetes indicate that something has gone wrong with the way a person makes or uses insulin. Diabetes is a disorder of blood sugar and insulin.

Insulin is a hormone made by the pancreas that lowers blood sugar by moving sugar out of the bloodstream and into the body’s cells. Insulin’s primary job is to keep blood sugar levels within a very narrow range. Insulin not only helps clear the excess glucose out of the blood, it also helps prevent muscle breakdown.1 However, it also increases fat storage, especially when blood levels are elevated, and prevents the body from using fat for fuel.

2. Types of diabetes

There are different kinds of diabetes, but all involve having too much sugar in the blood because the body is not making or using insulin effectively.

Type 2 diabetes

Type 2 diabetes is by far the most common form of diabetes, accounting for over 90% of all cases.2 In type 2 diabetes, the body usually does make some insulin, but can’t use it effectively.

Type 2 diabetes means the body has an increasingly hard time handling sugar in the blood. When the blood contains a lot of sugar, large amounts of insulin are produced. But, over time, too much insulin in the blood decreases the body’s ability to use insulin. This is called insulin resistance. When people are diagnosed with type 2 diabetes, they often have ten times more insulin in their bodies than normal.3

When insulin levels in your blood stay high for long periods of time, this can cause weight gain. Weight gain can be one of the first signs that the body is making too much insulin and is becoming insulin resistant.

Over time, the pancreas can no longer make enough insulin to keep blood sugar levels in check — even though it may still be making a lot! That’s because cells have become increasingly resistant to insulin’s effect. When this happens, blood sugar levels start to rise, and a person may be diagnosed with prediabetes or type 2 diabetes. When this happens, a diet that limits the foods that raise blood sugar the most can help.

Type 2 diabetes often affects people who are middle-aged or older, although it is becoming an increasing problem for teenagers and young adults in poor metabolic health. It’s not uncommon for the affected person to also have high blood pressure and other health problems.

Type 1 diabetes

Type 1 diabetes results when, for autoimmune or other unknown reasons, the pancreas becomes damaged and fails to produce insulin. This causes the high blood sugars that are also typical of type 2 diabetes. However, unlike people with type 2 diabetes, people with type 1 diabetes do not suffer from problems associated with excess insulin, such as weight gain. People with type 1 diabetes are, in fact, much more likely to be normal weight at diagnosis and experience rapid weight loss prior to receiving treatment.

Since people with type 1 diabetes make little to no insulin, treatment primarily consists of administering insulin with injections. In addition, a diet that doesn’t raise blood sugar can help people with type 1 diabetes achieve and maintain stable, normal blood sugar levels.

In the past, type 1 diabetes was often called juvenile-onset diabetes because it typically begins in childhood or when someone is a young adult. However, it can occur in older adults as well, often with a more gradual onset, which is referred to as LADA (Latent Autoimmune Diabetes in Adults, sometimes called type 1.5 diabetes). Regardless of one’s age at diagnosis, its effects last a lifetime.

Other types of diabetes

Sometimes a diagnosis of diabetes doesn’t fit neatly into the categories of type 1 or type 2. Some overweight adults develop type 1 diabetes, and thin people can develop type 2 diabetes. Gestational diabetes is a special case of type 2 diabetes that happens temporarily during pregnancy, although having gestational diabetes can make it more likely that you will develop type 2 diabetes later in life.4 There are also quite rare types of diabetes like MODY (Mature Onset Diabetes in the Young) and CFRD (Cystic Fibrosis Related Diabetes). Alzheimer’s disease is sometimes referred to as type 3 diabetes.5

3. Common symptoms of diabetes

  • Increased thirst and urination
  • Severe fatigue
  • Feeling hungrier than usual
  • Unexplained weight loss
  • Delayed healing of injuries
  • Blurred vision
  • Numbness and tingling in hands, feet or toes
  • Dark patches of skin
  • Skin rashes and lesions
  • Yeast and urinary tract infections (women)
  • Erectile dysfunction (men)

For more details about these conditions, see our guide to symptoms of diabetes. However, please note that with prediabetes and early stages of type 2 diabetes, you often don’t notice anything.

If you think you have any of the warning signs of diabetes, see your doctor.

4. How to measure your blood sugar

How do you know if you have too much sugar in your blood? Testing your blood sugar can help you find out. This test can be done in your doctor’s office or with your own inexpensive blood glucose meter.6

If you are testing your blood sugar at home, read and follow the directions that come with your blood sugar meter. For most meters, the general procedure goes like this:

  1. With clean hands, place a test strip in your blood sugar meter.
  2. Prick the side of a finger with the lancet to draw a drop of blood.
  3. Place the tip of the test strip on the drop of blood.
  4. After a few seconds, the blood sugar meter will give you a reading.

5. What are normal blood sugar levels?

Fasting blood sugar levels

If you check your blood sugar level first thing in the morning, before you eat, that is called a fasting blood sugar. You should check your blood sugar a few times, at the same time each morning to determine if your blood sugars are normal.

Normal fasting blood sugar is generally between 70 and 100 mg/dl (3.9 to 5.6 mmol/l).

If your fasting blood sugar is consistently between 100 and 125 mg/dl (5.6 to 6.9 mmol/l), you may have prediabetes, also known as impaired fasting glucose.

You may have diabetes if your fasting blood sugar is above 126 mg/dl (7.0 mmol/l) on two separate occasions.

Note that these values refer to fasting blood sugar levels in people who aren’t taking medication to control diabetes. If you have been diagnosed with diabetes and take insulin or oral medication, your fasting blood sugar may be below 126 mg/dl (7.0 mmol/l).

If you are already on a low-carbohydrate diet and you are concerned about the measurements you’re getting, see “How a low-carb diet affects blood sugar measurements.”

Post-meal blood sugar levels

A post-meal (also called “postprandial”) blood sugar is measured two hours after starting a meal. Measuring blood sugar after a meal can tell you if your blood sugar response to food is normal. As with fasting blood sugar measurements, you should check your blood sugar a few times to determine whether your levels are normal.

A normal post-meal blood sugar reading is below 140 mg/dl (7.8 mmol/l).

You may have prediabetes or impaired glucose tolerance if your post-meal blood sugar is above 140 mg/dl (7.8 mmol/l), but less than 200 mg/dl (11.1 mmol/l).

You may have diabetes if your post-meal blood sugar is above 200 mg/dl (11.1 mmol/l).

Again, note that these values refer to post-meal blood sugar levels in people who aren’t taking medication to control diabetes. If you have been diagnosed with diabetes and take insulin or oral medication, your post-meal blood sugar may very well be below 200 mg/dl (11.mmol/l).

If your blood sugar levels, either fasting or post-meal, are consistently higher or lower than normal, you may have a medical condition that requires a visit to a healthcare provider.

6. How food affects blood sugar

Sugar in your blood comes from two places: your liver and the food that you eat. You can’t do much to control the amount of sugar your liver makes, but you can control the kinds of food that you eat.

Food are made up of three broad categories known as macronutrients (major nutrients): carbohydrate, protein, and fat. Many foods are a combination of two or all three macronutrients, but we often group foods according to whether they are mostly carbohydrate, protein, or fat.


Of the three macronutrients, carbohydrate raises blood sugar the most — especially in people that have diabetes. Carbohydrate foods are ones that we typically think of as either sugary or starchy. Of course, some foods, like cake, are both!

Although very few people would agree that sugary foods are good for you, some foods that we think of as “healthy” — such as fruit — actually have a lot of sugar. And many people don’t know that starchy foods — such as bread, rice, pasta, and potatoes — quickly turn to sugar when you digest them. Eating a potato can raise blood sugar as much as eating 9 teaspoons of sugar!


Protein foods are foods like eggs, chicken, steak, and tofu. Although different people have different responses to some protein foods, consuming a moderate amount of protein at a meal generally has little effect on blood sugar.


Dietary fat has very little effect on blood sugar. However, we seldom eat fat all by itself. Some foods, like cheese, are made up of mostly protein and fat. Those foods are not likely to raise your blood sugar very much. But some foods, like donuts and French fries, are made up mostly of carbohydrate and fat. Because of their carbohydrate content, these kinds of foods are likely to raise your blood sugar.

7. Food for diabetes

What happens if you remove foods that raise your blood sugar from your diet? Is there anything good left to eat? We think so. In fact, we have a whole guide on “The best foods to control diabetes.”

But a picture is worth a thousand words. These are just a few of the delicious foods that don’t raise blood sugar:


Many people with type 2 diabetes are now choosing a diet based primarily on low-carbohydrate foods.7. And many doctors are recommending diets low in carbohydrates for their patients with diabetes.8 The American Diabetes Association has even said that reducing overall carbohydrate intake has demonstrated the most evidence for improving blood sugar levels for people with diabetes.9

Choosing foods low in carbohydrates is a safe and easy way to help you control your blood sugar. However, if you are taking medications for your diabetes, you must work with your healthcare provider to adjust your medications when you change your diet. Choosing a diet made up of food with fewer sugars and starches means that your blood sugar levels may improve quickly. The need for medications, especially insulin, may be dramatically reduced.

If you are looking for a doctor who will work with you to control your diabetes with a change in diet, our map may help you find one.

8. A message of hope

As recently as 50 years ago, type 2 diabetes was extremely rare. Now, around the world, the number of people with diabetes is increasing incredibly rapidly and is heading towards 500 million. This is a world-wide epidemic.

In the past, those affected by the most common form of diabetes, type 2, were told that they would never regain their health. Type 2 diabetes was thought to be a progressive disease with no hope for reversal or remission. People were — and sometimes still are — taught to “manage” type 2 diabetes, rather than to try to reverse their high blood sugars.

Unfortunately, “managing” type 2 diabetes often leads to an increase in medications and to serious complications: impaired vision, damaged kidneys, wounds that won’t heal, and decreased cognitive function. In many cases, these complications lead to blindness, kidney failure and dialysis, amputation, dementia, and death.

But now people with type 2 diabetes can hope to regain their health! Now we know that the hallmarks of type 2 diabetes — high blood sugar and high insulin — can be reversed. People don’t just have to “manage” their diabetes as it progresses. Instead, they can often lower their blood sugar to normal levels with diet alone. This means they can also avoid or even discontinue most medications.10

Normal blood sugar levels and fewer or no medications means no progression of disease, and no progression of disease means no complications. People with a diagnosis of type 2 diabetes may be able to live long, healthy lives, with toes, eyesight, and kidneys intact!

If you are not on any medications, you can start your journey back to health today. If you are on medications for diabetes or for other conditions, consult your doctor before beginning any lifestyle change, such as a low-carbohydrate diet, so that your medications may be adjusted safely as your blood sugars improve. When you’re ready, here’s where to start: A low-carbohydrate diet for beginners. During your own journey, you might be inspired by some spectacular diabetes success stories.

If you want to learn more about how you can improve your health and the health of your family, start here by keeping up with the latest news from Diet Doctor.