Blood sugar levels

and Eva Rudolf-Müller, doctor

Dr. med. Andrea Reiter is a freelance writer for the medical editorial team.

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Eva Rudolf-Müller is a freelance writer in the medical team. She studied human medicine and newspaper sciences and has repeatedly worked in both areas - as a doctor in the clinic, as a reviewer, and as a medical journalist for various specialist journals. She is currently working in online journalism, where a wide range of medicine is offered to everyone.

More about the experts All content is checked by medical journalists.

The blood sugar values indicate the sugar content of the blood. It changes during the day, depending on the food intake. Blood sugar levels rise after eating and are lowest in the morning after getting up. In some diseases, the regulation of the blood sugar level is disturbed. Read everything you need to know about blood sugar levels.

What are the blood sugar levels?

The energy supply of the cells is ensured by the blood sugar. The carbohydrates ingested with food reach the intestine, where they are broken down into smaller sugar molecules and absorbed into the blood. A hormone produced by the pancreas, insulin, ensures that the sugar is absorbed from the blood into the cells. It is the most important supplier of energy for the cells, in a sense their "fuel".

People whose pancreas do not produce enough insulin suffer from what is known as diabetes mellitus. Most of the time, your blood sugar level is too high. In the long run, this can damage the blood vessels and organs. At the same time, there is a lack of energy in the cells because the sugar cannot be channeled into the cells.

When do you determine blood sugar levels?

The blood sugar value is determined for various questions:

to diagnose diabetes (diabetes mellitus)
to control blood sugar levels in known diabetes mellitus
to control and adjust therapy in diabetics
annually in people who are at higher risk for diabetes
for symptoms that indicate diabetes (weight loss, thirst, frequent urination, decreased performance)
in pregnant women and newborns
if you suspect hypoglycemia or hypoglycemia
in the event of unconsciousness without an explainable cause
in case of malnutrition or malnutrition
with known disorders of the carbohydrate metabolism (e.g. due to enzyme deficiency)

How are blood sugar levels determined?

The blood sugar level is usually determined in the morning before the patient has eaten anything (fasting blood sugar). A drop of blood is obtained through a prick in the finger or the earlobe and applied to a small stick. The stick is then put into a blood glucose meter. After about half a minute, the device then displays the sugar content in the blood. The blood sugar level can also be determined as part of a normal blood sample.

Oral glucose tolerance test (oGTT)

If abnormal fasting blood sugar values (and / or other factors such as increased urination or extreme thirst) suggest diabetes mellitus, the oral glucose tolerance test (oGTT) can clarify:

First, the fasting blood sugar is determined. Then the patient drinks a precisely defined amount of a sugar solution. After two hours it is measured how high the blood sugar level has risen and how quickly it falls again.

Clearly increased values in the sugar test indicate diabetes. Then there are people who have not yet had diabetes, but who already have abnormal sugar levels. The sugar metabolism is already disturbed in them (preliminary stage of diabetes).

oGTT in pregnant women

An oral glucose tolerance test (oGTT) is routinely offered to pregnant women. The reason is that a small proportion of women develop diabetes during pregnancy. This gestational diabetes can cause serious complications for both mother and child. Therefore, as a precaution, all pregnant women should take the sugar load test between the 24th and 28th week of pregnancy (50g-oGTT as a preliminary test, 75g-oGTT). In this way, developing diabetes can be identified and treated at an early stage if necessary.

Blood sugar values table

The normal fasting blood sugar values depend on age:

Fasting blood sugar: normal values

up to 1 day

34 - 99 mg / dl

2 days

46 - 81 mg / dl

3 days to 17 years

60 - 99 mg / dl

from 18 years

74 - 99 mg / dl

Normal values in the oral glucose tolerance test

In the following table you can read from when the blood sugar values after eating and during oGTT (2 hours after drinking the sugar solution) are abnormally elevated, marginally elevated or normal:

Fasting blood sugar level

Occasional blood sugar levels (blood sugar levels after eating)

oGTT

(2h value)

Diabetes mellitus

≥ 126 mg / dl

≥ 7 mmol / l

≥ 180 mg / dl

≥ 10 mmol / l

≥ 200 mg / dl

≥ 11.1 mmol / l

Abnormal fasting sugar

100 - 125 mg / dl

5.6 - 6.9 mmol / l

140-199 mg / dl

7.8-11.0 mmol / l

Blood sugar levels normal

<100 mg / dl

<5.6 mmol / l

<130 mg / dl

<7.2 mmol / l

<140 mg / dl

<7.8 mmol / l

Attention: Depending on the measurement method, there are sometimes deviating standard values in the specialist literature.

When are the blood sugar levels too low?

In the following cases, the blood sugar levels are found to be too low:

Insulin overdose during diabetes therapy
Overproduction of insulin in pancreatic tumors (e.g. insulinoma)
Disorders of the hormonal balance due to an underactive pituitary gland, thyroid gland or adrenal cortex
after excessive physical work without adequate food intake
Malnutrition, for example in alcoholics, after excessive fasting or refusal to eat (anorexia nervosa)
severe liver damage, such as cirrhosis of the liver
after drinking alcohol on an empty stomach

A decreased blood sugar initially leads to hunger, dizziness, tiredness and sweating. If sugar is still not supplied, it can lead to seizures and circulatory collapse, including shock or death.

People with long-term diabetes often have few or no typical symptoms of hypoglycaemia and are therefore unable to take countermeasures in good time. You must therefore check your blood sugar levels regularly, especially if you are more physically active (for example during sport).

When are the blood sugar levels too high?

Elevated blood sugar levels can be caused by:

Diabetes mellitus
Gestational diabetes
Hormonal disorders caused by tumors in the adrenal medulla or tumors of the pituitary gland
Diseases of the pancreas
rare hereditary diseases
as a side effect of certain drugs

With high blood sugar levels, a feeling of thirst, visual disturbances and an increased urge to urinate often occur. There is also the risk of a life-threatening coma. In the long term, increased blood sugar damages the blood vessels. The consequences can be arteriosclerosis, kidney weakness, stroke and loss of vision. Serious tissue damage is also possible, for example on the lower legs and feet ("diabetic foot").

What should I do if my blood sugar levels change?

It is not uncommon for blood sugar to occasionally be a little below or above the normal value. This then has to do with food intake, physical activity or possible infections. Nevertheless, a blood sugar value that falls outside the norm should always be checked again. If necessary, additional values must be determined that can substantiate the suspicion of diabetes mellitus. In such a case, contact a diabetologist (an internal medicine specialist who specializes in diabetes). In addition, the family doctor will closely monitor the blood sugar values in the event of a disturbed sugar metabolism.

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