High blood sugar: symptoms and when to test

High blood sugar often creeps in unnoticed. Many women feel little for years while their fasting glucose slowly rises. That is exactly why it helps to know which signs go with it and when a blood test is useful.

I am writing this article because I notice that many people only think about their blood sugar once there are complaints. Below you will read what high blood sugar means, which symptoms can point to a raised value and which fasting glucose values count as too high under the common guidelines. You will also read when it is best to test your blood sugar and how you can arrange that yourself.

This article is meant as explanation and not as a diagnosis.

What does high blood sugar mean?

High blood sugar means there is more glucose in your blood than your body can process well at that moment. Glucose is the fuel for your cells, and the hormone insulin makes sure that fuel can get into them. When that system works less well, sugar stays behind in your blood.

In the short term a slightly raised blood sugar usually does no harm. If the value stays too high for a longer time, it can strain your blood vessels and nerves. A raised fasting glucose can be an early sign of insulin resistance, where your cells become less sensitive to insulin.

You can read more about that mechanism in our overview on insulin resistance in women and which blood values to test.

What are the symptoms of high blood sugar?

High blood sugar can cause complaints such as a lot of thirst, frequent urination, fatigue and sometimes blurred vision. Yet a slightly raised value often gives no symptoms at all. Because of this, high blood sugar sometimes goes unnoticed for a long time.

The classic complaints usually appear only at clearly high values. Think of a dry mouth, urinating more than normal, unintended weight loss and a tired or listless feeling. Wounds that heal more slowly or recurring bladder infections can also belong to it.

Important to know: these complaints are not proof. They also fit other things, such as the menopause, a thyroid problem or simply a busy period. Only a blood test shows whether your blood sugar is really too high.

Do you recognise vague, persistent complaints? Take them seriously, but do not draw a conclusion yourself yet.

Which values count as too high?

Whether your blood sugar is too high depends on your fasting glucose value in millimoles per litre (mmol/l). Roughly, a fasting value below 6.1 counts as normal, between 6.1 and 6.9 as raised and 7.0 or higher as fitting diabetes. The exact cut-off points can differ slightly per guideline and per laboratory.

The table below lists the common categories for fasting glucose. See it as a frame to understand your result better, not as a diagnosis.

These limits are reference values that match the explanation from sources such as the Diabetes Fonds and Thuisarts. Your laboratory always states its own reference values with your result, and those are decisive. A single raised value also says little, because your blood sugar fluctuates.

Besides fasting glucose, a doctor often also looks at your HbA1c, your long-term blood sugar. That value shows the average of the past weeks and nicely complements the single glucose measurement.

What can cause high blood sugar?

High blood sugar usually does not have a single cause, but arises from a combination of factors. Insulin resistance often plays a central role, where your body responds less sensitively to insulin. Genetic predisposition, weight around the belly and little movement increase the chance.

Hormones count too. With PCOS and around the menopause, the way your body handles sugar changes, so your blood sugar rises more easily. Gestational diabetes is another example, where blood sugar rises temporarily because of hormones from the placenta.

Furthermore, stress, lack of sleep and certain medicines such as corticosteroids can temporarily raise your blood sugar. That does not mean you have diabetes straight away. It mainly shows that your blood sugar is influenced by many things.

Are you pregnant or just gave birth? Then also read our article on the gestational diabetes test and which blood values belong to it.

When should you test your blood sugar?

It is sensible to test your blood sugar if you have complaints that fit a raised value, or if you are at increased risk. Think of diabetes in the family, being overweight, PCOS or a previous pregnancy with gestational diabetes. Even without complaints, a check around your fortieth can be useful.

For a reliable result you usually draw your glucose fasting, so after a night without eating. That way you compare your value with the fasting reference limits. Your GP can also request an HbA1c or a sugar test if there is a reason for it.

Are you unsure whether testing is useful for you? Then discuss your situation with your GP, who looks at your whole picture.

Testing your own blood sugar

If you want to map your blood sugar without first visiting your GP, you can do so at Lunara without a referral. You order the test online, draw fasting at one of the more than 750 draw locations in the Netherlands and get your result back digitally. Every result is assessed by a BIG-registered doctor.

The Diabetes blood test looks at your fasting glucose and your HbA1c, among other things. Together they give a broader picture than a single measurement: one shows your blood sugar at that moment, the other the average over the past weeks.

Testing yourself is a handy starting point, not an end point. You always discuss a raised or abnormal result with your GP, who decides whether follow-up is needed. That way you use the test for what it is good for: as an early signal and a basis for a conversation.

Frequently asked questions

What is a normal fasting blood sugar?

A fasting glucose below 6.1 mmol/l counts as normal under the common guidelines. Between 6.1 and 6.9 is raised and 7.0 or higher fits diabetes. Your laboratory always states its own reference values, and those are decisive.

Can you feel high blood sugar?

Sometimes, but often not. A slightly raised blood sugar usually gives no complaints, while clearly high values can cause thirst, frequent urination and fatigue. Because complaints are absent or vague, only a blood test shows how your blood sugar really stands.

Do I have to be fasting for a blood sugar test?

For a fasting glucose measurement yes, so after about eight hours without eating. You do not have to be fasting for an HbA1c, because that value is an average over weeks. The draw location will let you know what your test needs.

Does high blood sugar mean I have diabetes?

Not automatically. A single raised measurement can have various causes, from stress to a recent meal. The diagnosis of diabetes is only made after a repeat measurement or extra testing, always by a doctor.

How often should I check my blood sugar?

That depends on your risk and your earlier results. Without complaints or risk factors, regular testing is usually not needed. If you have an increased risk or an earlier raised value, your GP decides with you how often a check is useful.

References

1. Diabetes Fonds. Blood glucose values and testing for diabetes. Diabetes Fonds.
2. NHG and Thuisarts.nl. Type 2 diabetes and blood sugar values. Dutch College of General Practitioners.
3. Voedingscentrum. Blood sugar, carbohydrates and healthy nutrition. Voedingscentrum.

Every blood test result through Lunara includes a professional assessment by a BIG-registered doctor. This article is information and not a diagnosis or treatment advice. You always discuss a raised or abnormal result with your GP.