HEALTH TOPICS / TIREDNESS & ENERGY

Tiredness and low energy - what can a blood test show?

Most of it cannot be felt - but it shows in the numbers. A blood test can find or rule out the causes of tiredness that can be measured. No referral, at our clinic in Copenhagen.

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Tired all the time? You are not alone

According to the Danish patient handbook on sundhed.dk, tiredness is the reason for up to one in ten visits to a doctor. Most often it is linked to sleep, stress, a busy life or mental strain.

But in 20-25% of people who see a doctor about tiredness, a physical cause is found - such as anaemia, an underactive thyroid or diabetes. Some of these causes can be measured with a blood test.

A blood test cannot explain all tiredness. But it can answer a specific question: is there something in your blood that could explain why you lack energy?

What a blood test can measure

Blood

Haemoglobin

Haemoglobin shows whether you have anaemia - one of the most common physical causes of tiredness.

Iron

Iron and ferritin

Ferritin shows your body's iron stores and falls before any anaemia develops. Relevant with heavy periods, pregnancy or a plant-based diet.

Iron deficiency - symptoms and blood test (in Danish) →

Vitamins

B12 and folate

B12 deficiency can cause tiredness and memory problems, but the symptoms are not specific. That is why it takes a blood test to know.

B12 deficiency - symptoms and blood test (in Danish) →

Vitamins

Vitamin D

Low vitamin D is common in the winter months. A measurement shows your actual level, so any supplement can be targeted.

Vitamin and mineral deficiency →

Thyroid

TSH

TSH is the first marker when an underactive thyroid is suspected, which can cause tiredness, feeling cold and weight gain.

What TSH, T3 and T4 tell you →

Blood sugar

Long-term blood sugar (HbA1c)

HbA1c shows your average blood sugar over the past 2-3 months and is used to detect diabetes.

What a standard blood test shows →

Where should you start?

A good place to start

Basic blood test package

Haemoglobin, ferritin, B12, thyroid (TSH), long-term blood sugar and cholesterol - plus kidney and liver values - in one test.

DKK 1,599

Book a time
Vitamins and minerals

Vitamin and mineral balance

Vitamin D, B12, folate and full iron status plus minerals - the complete picture of your vitamins and minerals.

DKK 1,449

Book a time
Iron

Iron package

Full iron status, showing both whether you are short of iron and how far it has progressed.

DKK 749

Book a time
Thyroid

Thyroid

TSH, T3, T4 and free T4 in one package.

DKK 699

Book a time

These packages do not require fasting, and you can book whenever it suits you. See all packages and single tests on our blood test page.

When should you talk to your doctor?

If you have been tired for several weeks without an obvious explanation, talk to your own GP - even if you have a blood test with us. If the tiredness comes on suddenly and together with other symptoms, contact a doctor straight away.

We do not make diagnoses or carry out investigations. If a value is outside the normal range, we recommend that you follow up with your own GP. If a test shows a critical value, we will contact you.

Not sure what to choose?

Take the guide - ten short questions, and you have a suggestion. Or call +45 70 20 22 32.

Start the guide - 2 min.

NurseCare offers blood tests without a referral at the clinic at Rømersgade 3 in Copenhagen K - including the basic blood test package, vitamin and mineral balance, the iron package and the thyroid package. The sample is taken by experienced healthcare professionals, and you get your results on sundhed.dk, usually within 1-3 working days.

Book a blood test  See all blood tests

Are you a company? See blood tests for employees.

Frequently asked questions

The basic blood test package is a good place to start. It measures haemoglobin, ferritin, B12, thyroid (TSH) and long-term blood sugar, among others - some of the most common measurable causes of tiredness. For the full picture of your vitamins and minerals, choose vitamin and mineral balance.

Not always. Most tiredness is caused by sleep, stress or mental strain, which cannot be seen in the blood. A blood test can find or rule out physical causes such as anaemia, iron deficiency, B12 deficiency, an underactive thyroid and raised blood sugar.

No, not for the packages mentioned here. Fasting is only recommended when blood sugar (glucose) is measured. You can always book whenever it suits you.

If you have not started taking supplements yet, it makes sense to have the blood test first, so you know your starting point. If you already take supplements or medicine, tell us at your appointment - we will note it so the result can be assessed correctly.

You get your results on sundhed.dk, usually within 1-3 working days. If a test shows a critical value, we will contact you.

No. At NurseCare you book a time yourself, without a referral, at the clinic at Rømersgade 3 in Copenhagen K.

Sources (in Danish): Patienthåndbogen: Træthed - en oversigt · Lægehåndbogen: Træthed. Last checked 29 September 2026.

Clinically reviewed by Sanne Bjørk, Chief Nurse · Last updated 29 September 2026
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