Type 2 diabetes: Is it better to lower blood sugar levels to near-normal levels?

People with type 2 diabetes can prevent complications if they lower their high blood sugar levels permanently. Many doctors even recommend trying to get to near-normal blood sugar levels. But trials show that lowering blood sugar to near-normal levels can have both advantages and disadvantages compared with lowering blood sugar levels more moderately.

Diabetes mellitus is a metabolic disorder associated with high blood sugar levels. Blood sugar levels that are high for a long period of time can cause eye and kidney disease, for example. If diabetes is treated well, complications are less likely to happen. You can read more about the different types of diabetes, treatment options and how to deal with this metabolic disease in everyday life in our feature.

Type 2 diabetes typically affects people at an older age, but younger people can get it too. In this disease, insulin usually does not work properly on the body’s tissues and cells anymore. Insulin is what enables the tissues and cells to take up sugar. If this mechanism does not work properly, blood sugar levels rise. If there is too much sugar in the blood for years at a time, small blood vessels and nerves can be damaged. This can lead to eye and kidney disease as well as sensations of numbness, tingling or painful feet. There is also a higher risk of having a heart attack or a stroke.

Different recommendations for lowering blood sugar

Certain things can lower the risk of complications. Physical activity, losing excess weight and changing eating habits can all influence blood sugar levels. If these things do not lower blood sugar sufficiently, there are also drugs that can be taken. Some drugs that lower blood sugar can be swallowed in the form of tablets, and others can be injected under the skin. Which medications are most appropriate for you will depend on your health situation, among other factors. It is also important whether a medication helps you better than another one, or causes fewer adverse effects.

Experts agree that it is generally helpful for people with type 2 diabetes to lower their blood sugar levels. But what the best treatment is has been debated for many years, with the main question being what level blood sugar should be lowered to. On the one hand, treatment ought to prevent complications. On the other hand, its risk of adverse effects should be as low as possible.

By measuring the HbA1c level, doctors can find out whether blood sugar is being maintained at an adequate level over a longer period of time. This measurement shows the average blood sugar level over the last three months. There are different recommendations as to what HbA1c level should be considered the target. One recommendation is to aim at maintaining near-normal levels. This means that people with diabetes would have nearly the same blood sugar levels as people without this disease. People without diabetes usually have an HbA1c level of less than 6%, so doctors often advise people with diabetes to lower their blood sugar to levels below 6.5%. Other recommendations aim at levels between 6.5 and 7.5% or, in certain cases, even higher. The target level depends on the age of the people affected and any other illnesses they may have, among other things. Doctors tend to accept higher levels in older people who have not yet any symptoms that are typically associated with diabetes than in young people with type 2 diabetes.

One possible adverse effect of drug therapy is that blood sugar levels drop so low that they result in hypoglycemia. Episodes of mild hypoglycemia are associated with symptoms like trembling, suddenly feeling very hungry, sweating or a tingling sensation in the fingers and lips. If people have an episode of hypoglycemia, they can usually treat it themselves. Severe hypoglycemia is less common, but it can lead to impaired consciousness, seizures, breathing and circulation problems and other complications, some of which are life-threatening. You can read more about how type 2 diabetes can be treated in our feature.

Assessing different treatments

Researchers from the German Institute for Quality and Efficiency in Health Care (IQWiG) – the publisher of this website – together with researchers from the Graz University Hospital in Austria studied the benefit of lowering blood sugar to near-normal levels in comparison to a less-intensive approach. The researchers looked for trials comparing treatments for people with type 2 diabetes that had different goals: One group of people was to try to lower their HbA1c levels to below 7.5%. The other group was allowed to have higher levels. The trials specifically examined

• how many people died during the different treatments,
• which treatment led to fewer complications of diabetes, and
• how often adverse effects occurred during each of the treatments.

The researchers included seven trials with a total of almost 28,000 participants in their analysis. Depending on the trial, the average age was between 47 and 66 years. All participants had had type 2 diabetes for several years, and most of them were overweight.

No differences in important treatment goals

On the whole, none of the treatments was better than any of the others. In none of the trials did lowering blood sugar to near-normal levels lead to fewer people dying than lowering more moderately. Strokes, fatal heart attacks, kidney failure or amputations were not less frequent, either. There were not enough data on blindness and quality of life.

However, the trials did provide an indication that lowering blood sugar to near-normal levels can reduce the risk of non-fatal heart attacks somewhat. These occurred less often when blood sugar was lowered to a near-normal level than with more moderate treatment. On the other hand, there is a higher risk of adverse effects. The trials show that lowering blood sugar to near-normal levels more often leads to episodes of severe hypoglycemia and other severe complications. The more blood sugar levels were lowered, the more often these adverse effects occurred. On the whole, they occurred considerably more often than the non-fatal heart attacks that were then prevented.

On the basis of one of the large trials, the researchers estimated the probability of these events:

• About 100 people with type 2 diabetes would need to lower their blood sugar to near-normal levels over a period of 3.5 years in order to prevent one non-fatal heart attack in comparison to a more moderate lowering of blood sugar levels.
• In the same period of time there would be about 7 to 8 episodes of severe hypoglycemia caused by the intensive lowering of blood sugar in these 100 people.

Although there is a lot of uncertainty in these numbers, they still illustrate the two sides of the treatment: On the one hand, an intensive lowering of blood sugar levels can reduce the risk of non-fatal heart attacks. On the other hand, it raises the risk of severe hypoglycemia. People with type 2 diabetes generally benefit from lowering blood sugar levels that are both significantly and consistently too high. Yet the decision on how much they should be decreased can only be based on individual factors and has to be custom-tailored. It will probably help to talk this through with your doctor or your diabetes specialist.

Author: Institute for Quality and Efficiency in Health Care (IQWiG)


Note

This health information is a summary of a scientific report published by IQWiG. It is not an assessment of the right to have health care services paid for by statutory health insurance funds in Germany. By law, decisions about paying the costs for diagnostic and therapeutic procedures can only be made by the German Federal Joint Committee (G-BA). The Federal Joint Committee takes IQWiG reports into consideration in its decision-making process. You can find information about the decisions of the German Federal Joint Committee on its English-language website, www.english.g-ba.de.

© IQWiG (Institute for Quality and Efficiency in Health Care)