The aim of diabetes treatment is to bring blood sugar (“glucose”) as close to normal as possible. What are normal levels of blood sugar, and how can you achieve them?
First, what is the difference between “sugar” and “glucose”? Sugar is the general name for sweet carbohydrates that dissolve in water. “Carbohydrate” means a food made only of carbon, oxygen, and hydrogen.
There are various different kinds of sugars. The one our body uses most is called “glucose.” Other sugars we eat, like fructose from fruit or lactose from milk, are converted into glucose in our bodies. Then we can use them for energy. Our bodies also break down starches, which are sugars stuck together, into glucose.
When people talk about “blood sugar,” they mean “blood glucose.” The two terms mean the same thing.
In the U.S., blood sugar is normally measured in milligrams of glucose per deciliter of blood (mg/dl). A milligram is very little, about 0.00018 of a teaspoon. A deciliter is about 3 1/3 ounces.
In Canada and the United Kingdom, blood sugar is reported in millimoles/liter (mmol/L). You can convert Canadian or British glucose levels to American numbers if you multiply them by 18. This is useful to know if you’re reading comments or studies from England or Canada. If someone reports that their fasting blood glucose was 7, you can multiply that by 18 and get their U.S. glucose level of 126 mg/dl.
What are normal glucose numbers? They vary throughout the day. (Click here for a blood sugar chart.) For someone without diabetes, a fasting blood sugar on awakening should be under 100 mg/dl. Before-meal normal sugars are 70–99 mg/dl. “Postprandial” sugars taken two hours after meals should be less than 140 mg/dl.
Those are the normal numbers for someone without diabetes. If you have diabetes, the American Diabetes Association (ADA) advises keeping your blood sugar levels before meals from 80–130 mg/dl and your levels 1–2 hours after meals under 180. Many people with diabetes and doctors shoot for levels closer to those of people without diabetes, because they are more protective against complications. Lower numbers require more careful diet and more frequent monitoring to prevent lows, but they are doable for many people.
There is also a long-term glucose test called a hemoglobin A1c, HbA1c, or just A1C. This test gives your average reading over the last 2–3 months. HbA1c is expressed as a percentage. Normal for a person without diabetes is below 5.7%. Targets for a person with diabetes recommended by the ADA are 7.0% or lower if you want tight control.
When glucose levels get higher than normal, they start to cause inflammation in blood vessels and nerves. This is where all the complications of diabetes come from. So you don’t want high blood glucose levels.
In people without diabetes, normal insulin function keeps sugars in a normal range. When you have diabetes, insulin function is damaged. You need to give your body conscious help, by eating right, exercising, taking medications or herbs, and reducing stress.
Low blood sugars are also a potential problem. If you take insulin or a sulfonylurea or meglitinide drug, there is a risk of your blood sugar going too low. Low blood sugar (“hypoglycemia,” pronounced high-po-gleye-SEEM-e-uh) can cause dizziness, confusion, or fainting.
Normal blood glucose numbers
Normal for person without diabetes: 70–99 mg/dl (3.9–5.5 mmol/L)
Official ADA recommendation for someone with diabetes: 80–130 mg/dl (4.5–7.2 mmol/L)
2 hours after meals
Normal for person without diabetes: Less than 140 mg/dl (7.8 mmol/L)
Official ADA recommendation for someone with diabetes: Less than 180 mg/dl (10.0 mmol/L)
Normal for person without diabetes: Less than 5.7%
Official ADA recommendation for someone with diabetes: 7.0% or less
Testing your blood sugar
You can learn what your blood glucose is at a given moment with a fingerstick blood test, using any available glucose meter. It hurts a little, and the test strips cost money, but you can get good information. You can reduce the pain and the hassle of needle sticks and get more information with a continuous glucose monitor or CGM. CGMs measure from a sensor inserted under the skin, often on the abdomen. (Currently, CGMs need to be calibrated roughly twice a day with a conventional blood sugar monitor.)
For people taking rapid-acting or intermediate-acting insulin, blood sugar testing should be frequent. You want to take the right amount and not have your blood sugar go too low.
For people with Type 2 diabetes who are not on insulin, how much to test is up to you. If you’re trying for tight control, you can test after eating different foods and doing different activities to see how they affect your glucose. Keep careful records of your results and perhaps log what you were eating and doing before your test.
It doesn’t help much to test at the same time every day, usually on waking and before dinner. Test with a plan; when you change something like a new medicine dose or an herb, then test in the days afterward. Many monitors keep your result records for you or send them to your computer or your doctor.
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