Diabetes is a disease characterized by elevation of blood glucose (a sugar) caused by decreased production of the hormone insulin and/or increased resistance to the action of insulin by certain cells. Glucose is the body’s main fuel. When you eat carbohydrates (pasta, bread, rice, grains, fruits, and vegetables), your digestive system breaks them down into glucose, which is released into the bloodstream so your body can use it for energy. Glucose also gets stored in the liver as glycogen, which can later be broken down back into glucose when the body needs fuel.
Insulin, which is produced in the pancreas, regulates both the movement of glucose into the body’s cells and the breakdown in the liver of glycogen into glucose. Both actions are critical to keeping blood sugar levels within normal ranges.
Type 1 v. Type 2
About 1.5 to 2 million people in the U.S. have a form of the disease called type 1 diabetes. In this condition — usually diagnosed in childhood or the early teen years – the pancreas, over a relatively brief period of time, stops producing insulin altogether. The onset of the disease is usually abrupt, with severe symptoms that require immediate attention. Type 1 diabetes is an “autoimmune” disease, which means the body attacks itself. Specifically, aberrant immune cells damage and destroy the part of the pancreas that produces insulin. People with type 1 diabetes must inject insulin every day.
In type 2 diabetes, the pancreas produces enough insulin, at least in the early years of the disease. But for reasons that are still not well understood, the body’s cells become resistant or insensitive to it. To compensate, the pancreas pumps out increasing amounts of insulin to normalize blood glucose levels. Over time — as long as a decade — this ever-increasing production becomes unsustainable, and the pancreas’ ability to produce insulin declines.
As a result, the telltale marker — and problem — of diabetes emerges: glucose levels rise in the blood because it is unable to enter the body’s cells. The excess glucose is damaging to the body’s tissue and leads to the symptoms and complications of diabetes. When the blood glucose level gets high enough, the sugar begins to appear in the urine and causes increased urination.
Elevated blood sugar puts a strain on almost every organ and other parts of the body. Over years, it is particularly toxic to the body’s blood vessels; it causes them to thicken. This leads to problems in the eyes and kidneys, the heart, the liver, and the blood circulation system. High blood sugar also damages the nerves. Proper treatment that keeps blood sugar in the normal range sharply reduces the risk of these complications.
There is a disagreement in the medical community about whether all adults should have their blood sugar checked periodically. The American Diabetes Association advises that everyone aged 45 and over have a blood sugar test once every three years. But the highly regarded U.S. Preventive Services Task Force says not enough scientific evidence exists to show that such broad screening has benefits or is worth the cost.
We think the decision rests with you and your doctor, and depends on an assessment of your overall health, risk factors, weight, and family history. Some doctors are inclined to check the blood sugar levels of most people over age 45 or 50, especially if they are 10 or more pounds overweight. Other doctors may be more conservative.
The symptoms of type 2 diabetes tend to develop gradually over time and include:
These symptoms can also be mild and/or intermittent for years. If you experience any of these — and especially if you experience two or more, for even a few days — you should see a doctor.
Again, there are many theories and ideas about the causes of type 2 diabetes, and the insulin resistance that characterizes it. Studies show the disease runs in families, meaning it has a strong genetic (hereditary) component. Another cause is being overweight or obese. In some cases, this can occur due to a genetic propensity, but in most cases it is due to overeating and lack of exercise. About 55 percent of people diagnosed with diabetes in the U.S. are overweight or obese.
While recent media attention surrounding the diabetes epidemic has focused on its link to obesity, the statistic above shows that 45 percent of people with diabetes are not overweight, meaning that there are other causes of the disorder.
In the early stages of the disease, symptoms may be nonexistent. That’s unfortunate because the damage to organs occurs even in the absence of symptoms. For this reason, it’s important for people who may be at risk for diabetes to get their blood sugar levels checked regularly. Those at risk include:
If you are in one of these groups and have never had a blood sugar check, get it tested as soon as possible.
What is Pre-Diabetes?
In the last decade, doctors and researchers have recognized that a large number of people in the U.S. have fasting blood sugar levels that are above 110 mg/dl (the upper limit of normal) but less than the 126 mg/dl required for a diagnosis of diabetes. The most recent estimate from the Centers for Disease Control and Prevention indicates that 35 percent of adults 20 and older — 79 million people — have blood glucose levels in this range and thus have what is called prediabetes. (It’s also sometimes called borderline diabetes or impaired fasting glucose.)
What concerns doctors is that a growing body of research now shows that people with pre-diabetes have (a) a very high risk of developing diabetes, and (b) an elevated risk of heart disease and stroke even if their glucose level never rises above 126 mg/dl.
In an analysis involving 10,428 people in Australia, those with prediabetes were found to have 2.5 times the risk of dying from heart disease over a 5-year period compared to people whose blood sugar was normal.
Such findings are leading many doctors to consider drug treatment for people with pre-diabetes. But most doctors agree, and research backs it up, that dietary and lifestyle changes can be very effective for keeping pre-diabetes under control — before any medicines need to be prescribed.
That said, this report does not specifically address treatment of pre-diabetes. If you are diagnosed with pre-diabetes we would urge you to talk with your doctor about ways to alter your diet and lifestyle, and lose weight if you need to.
Metformin, Metformin Sustained Release (generic of Glucophage)
Cost: $14-$35/mo (SR $8/mo)
Glipizide, Glipizide Sustained Release (generic of Glucotrol)
Cost: $4-$5/mo (SR $10-$20/mo)
Glimepiride (generic of Amaryl)
All these medicines are available as low-cost generics, either alone or in combination. (See Table 5.) In recent years, a strong medical consensus has emerged in the U.S., Europe, and Australia that most newly diagnosed people with diabetes who need a medicine should first be prescribed metformin.
Based on the systematic evaluation of diabetes drugs that forms the basis of this report, we concur with that advice. Unless your health status prevents it, try metformin first. If metformin fails to bring your blood glucose into normal range, you may need a second drug. Most commonly that should be one of the two other Best Buys we have chosen.
If you are unable to take metformin or do not tolerate it well, you face a choice of one of the sulfonylureas or a newer medicine as your first line medicine. Despite the elevated risk of hypoglycemia, we recommend trying glipizide or glimepiride. If glipizide or glimepiride alone fail to bring your blood glucose into control and keep your HbA1c at or below 7 percent, your doctor will likely recommend a second drug.
This report focuses on six classes of pills. We evaluate and compare the drugs in all six groups. We do not evaluate injectable drugs, including the newest ones, exenatide (Byetta) and liraglutide (Victoza). We also don’t compare diabetes pills with treatment with insulin or combination treatments consisting of injectable drugs.
Note that even though most people prefer to avoid injections, insulin and other injectable diabetes drugs often become necessary if diet, exercise, and pills fail to keep blood sugar under control.
How do they work?
The six types of diabetes medicines work in different ways. But they all: (a) lower blood sugar levels, (b) help improve the body’s use of glucose, and (c) decrease the symptoms of high blood sugar.
Since the drugs work in different ways, they are sometimes used in combination to enhance the effectiveness of treatment. Indeed, more than 50 percent of people with diabetes who start taking one type of medicine will need another type (or insulin) within three years to keep their blood sugar under control. But all will also need to alter their diets and lifestyles as well — losing weight if needed, making dietary changes (such as cutting back on carbohydrates), quitting smoking, and becoming more physically active.
Our evaluation leads to the following overall conclusions:
All the diabetes medicines can have side effects. These vary from drug class to drug class and medicine to medicine. Generally, the risks posed by diabetes drugs are not an impediment to using them if you truly need one.
Even so, side effects can keep people from taking their diabetes pills. On average, 10 to 20 percent of people with diabetes stop taking their pills due to side effects. It's important to discuss any side effects you experience with your doctor.
Most notably, some diabetes drugs can cause low blood sugar, or hypoglycemia. This is a dangerous side effect and one that leads some doctors to prescribe one diabetes drug over another. The symptoms of hypoglycemia are listed in the box on this page. Unfortunately, some people do not have minor symptoms to warn them that their blood sugar is getting dangerously low. That’s one reason your doctor will emphasize to you that you must check your blood sugar regularly.
Another worrisome side effect of some of the diabetes drugs is weight gain, or difficulty losing weight. Since many people with diabetes are trying to lose weight, this side effect can also be very frustrating.
Don’t take Avandia; Actos a Last Resort
One of the newer classes of drugs poses an elevated risk of heart failure. Evidence overwhelmingly indicates that the thiazolidinediones — Avandia (more about this drug below) and Actos — pose a 1.5 to 2 times increased risk of congestive heart failure compared to other diabetes medicines. Between 1 and 3 people in 100 without a history of heart disease will develop the condition if they take one of these drugs. In contrast, metformin and the sulfonylureas do not raise the risk of heart failure in any significant way compared to the general risk of this condition among people with diabetes, which is higher than normal.
Because of the clear evidence of heart failure risk, both Actos and Avandia carry a high-profile “black box” warning about it on their labels (guidance to doctors and patients on how to use them). If you are taking one of these medicines and have swelling of any part of your body, sudden weight gain, or breathing problems, you should contact your doctor immediately.
In addition to heart failure, Avandia also increases the risk of heart attack and stroke. For that reason, the FDA has restricted use of the medication (and combination products that contain it) only for people who have persistent high blood sugar levels even after taking another medication and who can’t take an alternative such as Actos. Avandia and combination products, Avandamet and Avandaryl, are no longer available at pharmacies. Instead, if you need one of those medications, both you and your doctor have to register with a special program to have them delivered by mail-order.
If you are already taking Avandia, Avandamet, or Avandaryl, and they are working to control your blood sugar, you can continue to take them, but we strongly recommend you discuss with your doctor whether they are appropriate for you.
Both Actos and Avandia have also been linked to a slightly increased risk of fractures of the upper and lower limbs, such as the wrist or ankle, in women. The risk was small — about 2 percent higher in people taking Avandia or Actos compared with those taking other diabetes drugs, according to preliminary studies.
Actos increases the risk of bladder cancer in people who take it for a year or longer. The risk applies to all drugs containing pioglitazone, including Actoplus Met, Actoplus Met XR, and Duetact. France banned Actos and combination pills due to the cancer risk.
Our medical advisors say that people with diabetes should use Actos only as a last resort, which means only if all other options have failed. People who have previously had or currently have bladder cancer should not use Actos or the combination pills that contain it at all.
Evidence strongly supports the additive effect of lifestyle changes plus medicines. But several studies also show that many people with diabetes can lower their blood sugar levels almost as much with lifestyle changes alone as with medicines, especially in the early stages of their disease.
Thus, given that (a) all the diabetes drugs have the potential to cause side effects and (b) lifestyle changes have benefits to your health beyond controlling blood sugar, most doctors will recommend you try diet and lifestyle modifications first — before you try a drug.
Many people with diabetes, however, also have high blood pressure and/or elevated cholesterol, or have been diagnosed with coronary artery or vascular disease. If you are in this category, your doctor may prescribe a diabetes drug when you are diagnosed, along with diet and lifestyle changes and classes in diabetes self-management.
Consumer Reports. Best Treatments for Type 2 Diabetes. We compare the safety, effectiveness, and price of the most common drugs for this condition. Published December 2012.