Dr Aidin Rawshani

Blood sugar and HbA1c: normal values, target values and limit values

Contents

Normal values, target values and maximum levels for blood sugar and long-term blood sugar (HbA1c)

Over 400,000 Swedes have type 2 diabetes and a lot of people have diabetes without knowing it. Symptoms of type 2 diabetes can be very unobtrusive. Anyone who has diabetes, or suspects it has diabetes, should know which blood glucose values are to be considered as “good” or “bad”. People with diabetes should always monitor their blood sugar, from the first day the disease is diagnosed. The better you have on your blood sugar, the better you have to control it. The aim is to reduce blood sugar and thus reduce the risk of future complications without suffering from hypoglycaemia (low blood sugar).

Your healthcare provider will prescribe blood tests to regularly check your blood sugar levels and long-term blood sugar (HbA1c). The HbA1C test reflects blood sugar levels over the last two to three months. However, in order to best manage your diabetes and adjust your treatment as needed, you also need to monitor your own blood sugar levels on a daily basis. The exact schedule of blood glucose measurement depends on several different factors.

Read also our review of Blood sugar, HbA1c and blood sugar measurement.

How to measure blood sugar?

To measure your blood sugar, you need a blood glucose meter. If the medical center or medical clinic has not offered you a blood glucose meter, you can buy one at the nearest pharmacy. Several excellent glucose meters cost less than 300 SEK and, as a rule, there is no need to buy a more expensive one (some glucose meters cost more than 1,000 SEK). In addition to glucose meters, a test stick and lancette are also needed. Using the lancette, you stick a hole in the finger and then transfer a drop of blood to the stick that is fed into the blood sugar meter.

How to check your blood sugar

The following steps contain general guidelines for testing blood sugar levels. However, since the instructions may vary from device to device, it is best to check the package leaflet for your glucose meter or talk to your healthcare provider. It is important never to share surveillance equipment or fingerstick devices, as this can lead to infection.

  • Wash your hands with soap and warm water, then wipe your hands and fingers.
  • Prepare lancet. Lancets used more than once are not as sharp as a new lancet and can cause more pain and damage to the skin.
  • Prepare the blood glucose meter and test strip (the exact instructions for this depend on the type of glucose meter used).
  • Use the lancet to collect a small drop of blood from the tip of the finger or alternative place (like the skin on the forearm).
  • Alternative places are often less painful than the tip of the finger. However, the results from alternative locations are not as accurate as samples from the fingertip.
  • When your blood sugar rises rapidly (e.g. immediately after eating) or falls rapidly (in response to insulin or exercise), it is more accurate to use your fingertip, as measurement in alternative locations can produce significantly different results in these situations.

If you find it difficult to collect a drop of blood from your fingertip, try to rinse your fingers with warm water and shake your hand below the waist. This can help make the blood flow right to the tip of the finger.

  • Apply the drop of blood to the test strip in the blood glucose meter. The results are displayed on the meter after several seconds.
  • Discard the used lancet in a container designed for sharp (not in kitchen towels) items.

Blood glucose meters

There is no single blood glucose meter that is better than others. Your caregiver or pharmacist can help you choose a meter based on your preferences as well as other factors such as cost, ease of use and accuracy. Many insurance providers cover the cost of specific meters and/or supplies.

Blood glucose meter in the home

Blood glucose meters are reasonably accurate, however, there may be some variation between each blood glucose meter. If you get a result that doesn’t match how you feel (for example, if your blood sugar is very low but you have no symptoms), check your blood sugar level again or use an alternative method to test your blood sugar (e.g. another meter). Blood glucose meters also work worse under conditions of low blood sugar.

When do you get the test answer?

The blood test is usually analyzed at reception where it is measured and then you will get answers right away. If the reception does not have a machine that can interpret the blood sample, the sample will be sent to a laboratory where it will be analyzed and you will receive the answer within a few days.

Limit values for blood sugar

If you measure blood sugar by sticking your finger, you take a so-called capillary sample, because the blood then comes from the smallest blood vessels (called “capillaries”). In the medical center, they often take samples directly from veins in the arms and then it is called a venous sample. The limits for diabetes in veins and capillaries differ and, in addition, there are limits for blood sugar after a so-called glucose load. A glucose load is a test that you perform by drinking 75 g of sugar and then measuring blood sugar. The following table shows all limit values. Note that maximum levels for pre-diabetes are also specified. Pre-diabetes is a precursor to diabetes.

Different blood sugar levels

  • Normal blood sugar is max 6.0 mmol/l.
  • Blood sugar between 6.1 mmol/L to 6.9 mmol/L is called “pre-diabetes”, which is a precursor to diabetes. Thus, between 6.1 and 6.9 is considered abnormal.
To diagnose “Diabetes”Glucose concentration in plasma (mmol/L)
 Venous testCapillary test
Values during fasting

 

Values 2h after glucose-load

≥ 7,0

 

≥ 11,1

≥ 7,0

 

≥ 12,2

Impaired glucose tolerance (for diagnosing “Prediabetes”)
Values during fasting

 

Values 2h after glucose-load

< 7,0

 

≥ 7,8 och < 11,1

< 7,0

 

≥ 8,9 och < 12,2

Most often, the sample is taken during fasting, which means that you are not allowed to eat food for 8 hours before the test. In order to be diagnosed with diabetes, two values should be above the limit value. If fasting is not possible, you can take a ‘random’ sample, which means that you can take the sample at any time of the day, but the maximum level is 11.1 mmol/L.

What is glucose load (OGTT)?

If you are unsure of the diagnosis, you can do a glucose load, which means that you are allowed to drink 75 g of glucose (after fasting). You measure blood sugar just before drinking the sugar solution and after 2 hours.

Use of HbA1c to diagnose diabetes

HbA1c is also called long-term blood sugar. Actually, HbA1c is the proportion of hemoglobin that is “sugared”. The higher the blood sugar you have, the more hemoglobin is sugared. Hemoglobin is a protein in the body that is contained in our red blood cells and allows it to transport oxygen into the blood. So people with diabetes have high HbA1c. Actually, HbA1c reflects blood sugar in the last 2 to 3 months. HbA1c is thus “average blood sugar” in the last 2 to 3 months.

In Sweden, HbA1c is indicated in the unit mmol/mol, but abroad a percentage (%) is often used.

Limit values for HbA1c

  • Normal: less than 42 mmol/mol (6.0%)
  • Pre-diabetes: 42 to 47 mmol/mol (6.0 till 6.4%)
  • Diabetes: 48 mmol/mol (6.5%) or higher
The red blood cells shown in the picture contain the protein hemoglobin that binds to oxygen. Sugar (glucose) reacts with hemoglobin and attaches to it and is measured in blood tests such as HbA1c.

Target values: what is a good blood sugar/HbA1c?

The purpose of measuring blood sugar is to reduce the risk of acute complications (hypoglycemia, hyperglycemia) and long-term complications (retinopathy, neuropathy, nephropathy, coronary heart disease, heart failure, etc.). Today, in fact, people prefer to measure HbA1c instead of blood sugar. This is because blood sugar varies very much from hour to hour and therefore an individual sample may be misleading. HbA1c does not affect from one hour to the next. HbA1c instead reflects the average blood sugar in the previous 2 to 3 months. Your current HbA1c is most characterised by the levels in the last 30 days. The last 60 days determine approximately 80% of your HbA1c.

Convert blood sugar, HbA1c and average blood sugar

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Remember that HbA1c reflects how much hemoglobin is “sugary”. It takes several steps for glucose to attach to haemoglobin and there is some individual (and ethnic) variation in the effectiveness of this process. However, individual and ethnic variations are rather small and at the moment nothing to worry about. HbA1c should be considered as a safe indicator of the mean level of blood sugar in the last 2 to 3 months.

Recommended target values for HbA1c according to the Swedish Association for Diabetology

Type Optimal controlAcceptableUnsatisfactory
Type 1≤ 5252-62> 62
Type 2≤ 4242-52> 52

Blood sugar levels and complications

The limit values seen in the table are based on the risk of complications. At these values (optimal control), the risk of complications is the least, without the risk of hypoglycemia being unnecessarily high. However, it should be mentioned that eye damage (retinopathy) in type 1 diabetes actually occurs at 48 mmol/mol, which means that optimal control would actually be 48 mmol/mol (and not 52 mmol/mol).

The reason that target values are higher for people with type 1 diabetes is simply because it is more difficult to reach lower levels without risking hypoglycaemia. It is important to point out two things:

  1. The purpose of lowering blood sugar is to reduce the risk of diabetic complications.
  2. The target value must be adapted to the individual.

The objective must be individualised. Your ability, motivation, age, other illnesses, prerequisites, etc., must all be taken into account.

In order to reduce the risk of eye damage, kidney damage and nerve damage, HbA1c should preferably be kept below 48 (average blood sugar 7.8, fasting blood sugar below 6-8 mmol/l and daytime below 10 mmol/l) to an optimal value. At higher values, the risk gradually rises. This applies to both type 1 and type 2 diabetes.

High HbA1c is also associated with an increased risk of coronary heart disease, heart attack, stroke, heart failure, peripheral vascular disease, etc. Although it has been more difficult to prove that high blood sugar actually causes these complications, more and more research suggests this.

DCCT-studien. A1c 7% = 52, 8%= 63, 9% = 73, 12% = 104
The following graph (taken from the Diabetes Manual) shows how the risk of various diabetic complications rises with higher HbA1c values.

How often should you measure blood sugar?

Studies have shown that people with diabetes who have normal or almost normal blood sugar levels reduce the risk of diabetes-related complications such as heart attack, stroke and heart failure.

How often you need to control your blood sugar depends on the type of diabetes you have (type 1 or 2), the treatment (s) you are taking (oral medicines, insulin and/or lifestyle changes) and your treatment goals. Normally, you should check your HbA1c every three to six months. This can be done more often if your blood sugar levels fluctuate rapidly for a short time.

Type 1 diabetes

For people with type 1 diabetes, frequent blood sugar measurement is the only way to safely and effectively control blood sugar levels. Most need to test at least four times a day. If you are using an insulin pump, you need three or more insulin injections per day, or if you are pregnant with type 1 diabetes, you may need to test as many as 10 times a day or more.

People who test frequently, especially those who have applied intensive insulin therapy (i.e. multiple doses of insulin per day or an insulin pump), may consider continuous glucose monitoring (CGM) (see chapter on technology equipment in diabetes). If you do not use CGM, you can buy several blood glucose meters to have at home, at work, school and/or in a purse or backpack. This way you will be able to access your test equipment wherever you are, making it easier to keep your blood sugar under control.

Type 2 diabetes

For people with type 2 diabetes, the frequency of testing of blood sugar is based on individual factors such as type of treatment (oral medications, insulin and/or lifestyle changes), HbA1C levels, risk of hypoglycaemia (when blood sugar is too low) and treatment goals.

Blood glucose monitoring is useful among people with type 2 diabetes taking insulin or certain medications that can cause hypoglycemia. It is generally unnecessary in people who deal with their diabetes with only diet or who take medications that do not cause hypoglycemia. Your healthcare provider can help you determine how often you should check your blood sugar based on your situation.

Interpreting blood glucose values

Blood sugar tests

The results of blood glucose measurements show how well your diabetes treatments work. However, blood sugar results can be affected by various things, such as your level of physical activity, what you eat, stress and medicines (including insulin and oral diabetes medicines). To fully understand what your blood sugar levels mean, it is important to take into account all these factors.

When you keep track of your results, you should include the time and date, blood sugar results, as well as the medication and dose you are taking. In addition to this, you need notes about what you ate, whether you have exercised, and any difficulties with illness or stress that can also be helpful. You should review this information regularly with your healthcare provider to understand what your results mean and if you need to make any changes to better manage your blood sugar.

Need for urine tests

If you have type 1 diabetes, your healthcare provider will talk to you about controlling your urine for ketones. You will need to check the ketones if your blood sugar levels rise to 13.9 — 16.7 mmol/l, during periods of illness or stress, or if you show symptoms that suggest ketoacidosis (such as nausea, vomiting and abdominal pain).

Ketones are acids that are formed when the body does not have enough insulin to get glucose into the cells, causing the body to break down fat for energy. Ketones can also develop during illness, if an insufficient amount of glucose is available. Ketoacidosis is a condition that occurs when high levels of ketones are found in the body; it can lead to serious complications like diabetes coma.

Checking ketone levels in the urine is done with a measuring stick, available in pharmacies without a prescription. If you have moderate to large levels of ketones, you should immediately contact your health care provider to determine the best treatment. You may need to take an extra dose of insulin, or your healthcare provider will allow you to go to the nearest emergency room. Meters that measure ketone levels in the blood are also available, but because of their cost, urine tests are used more widely.

Target value for people with type 2 diabetes

The following figure shows how HbA1c develops in the first 10 years with type 2 diabetes. Graphene includes the majority of Swedes with type 2 diabetes, and it is divided by birth region.

Denna graf visar hur HbA1c utvecklas under de första 10 åren med diabetes. Grafen är uppdelad efter födelseregion och inkluderar majoriteten av alla svenskar med typ 2 diabetes. Källa: Rawshani et al, BMJ Open. Licens: Open Access.
This graph shows how HbA1c develops in the first 10 years of diabetes. Graphene is divided by birth region and includes the majority of Swedes with type 2 diabetes. Source: Rawshani et al, BMJ Open. License: Open Access.

This graph shows a phenomenon faced by people with type 2 diabetes. In the beginning, the HbA1c value is fairly easy to control and this is because you often have your own insulin production. However, over the years, beta cells (which make insulin) become tired and eventually they stop, and then the body’s own production of insulin decreases or stops. Gradually, blood sugar rises and the risk of complications increases. At the same time, some people with diabetes may experience something called “diabetes burnout” which means that after many years of illness you begin to get tired of the disease and thus become less accurate. This is a challenge for people with type 2 diabetes because blood sugar is very likely to increase over time.

People who have recently been diagnosed, as a rule, have their own production of insulin. Intensive reorientation of the diet (for example, to LCHF or Mediterranean diet) and physical activity can be enough to normalize blood sugar! Metformin (tablets) is often offered and these have strong scientific support. Metformin reduces the risk of diabetic complications without increasing the risk of hypoglycaemia. The vast majority of people with newly diagnosed diabetes should bet on achieving a blood sugar.

If you reconsider your diet (especially low-carbohydrate diet like LCHF) and start with metformin and physical activity, you will likely get good HbA1C values and many will make the mistake that they reduce the number of metformin tablets. This is a cardinal error. Metformin should be retained.

Key to getting a good blood sugar/HbA1c is weight loss. The fact is that weight loss can lead to being cured. Today it is no longer acceptable to assume that the disease is chronic; many can be cured, especially if they have not had the disease location.

Type 1 diabetes

People with type 1 diabetes do not have their own production of insulin and are therefore completely dependent on insulin syringes. To regulate blood sugar in type 1 diabetes is therefore more difficult and for the same reason many more people with type 1 diabetes are offered advanced equipment such as continuous glucose meter and insulin pump. As a rule, these give improved HbA1c, compared to insulin pens.

Elderly and seriously ill

It is not reasonable to strive for optimal blood sugar values if you are old or sick. It can involve risks and it is doubtful whether it adds anything. A blood sugar up to 15 mmol/L is not disturbing and can be accepted if you are old or seriously ill. At higher values, you get tired and have pronounced symptoms of diabetes.

Low blood sugar values

A long-term blood sugar (HbA1c) around 25-30 mmol/mol indicates that you have a low average blood sugar level if you are otherwise healthy.

Symptoms of low blood sugar can cause problems such as hunger, nervousness, sweating, dizziness and even confusion. If not treated, low blood sugar (also called hypoglycaemia) can lead to loss of consciousness, seizures, coma or death. Low blood sugar levels begin at 3.0—3.5 mmol/l or less. Patients who have had diabetes for many years sometimes do not feel the adrenergic symptoms (palpitations, tremors, sweating, etc.) and may suddenly become unconscious.

People with diabetes who take too much medication (insulin or oral medicine) or take their usual amount but then eat less or exercise more than usual may develop hypoglycaemia. Although very rarely, hypoglycaemia may develop in some people without diabetes when taking someone else’s medication, have excessive alcohol consumption, develop severe hepatitis or develop a rare tumor of the pancreas (insulinoma).

The treatment for hypoglycemia is oral glucose intake (15 grams of sugar, for example, 1 tablespoon of sugar, honey, corn syrup or IV liquids containing glucose. Check your blood sugar level again within about 15 minutes after treatment is recommended. A low or unexpected low value if you have diabetes may also be because you have red blood cells that break more easily than others.

Symptoms of hypoglycaemia

Early signs and symptoms of diabetes hypoglycemia include:

  • Shaking
  • Dizzy
  • Sweating
  • Hunger feeling
  • Irritability, anxiety or aggression
  • Nervousness
  • Headache

Nocturnal symptoms

Diabetes hypoglycemia can also occur while sleeping. Signs and symptoms, which can awaken you, include:

  • Wet sheets or bedding due to sweat during night
  • Fatigue, irritability or confusion on awakening

Symptoms of pronounced hypoglycemia

If diabetes hypoglycaemia goes untreated, signs and symptoms of severe hypoglycaemia may occur. These include:

  • Clumsiness or jerky movement
  • Muscle weakness
  • Difficulty speaking
  • Blurred vision or double vision
  • Drowsiness convulsions or seizures
  • Loss of consciousness
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