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How do vitamin D tests work?

Updated: Nov 20, 2023

When it lacks enough vitamin D, the human body cannot adequately absorb calcium or maintain a healthy bone structure and immune system. At the same time, the symptoms of vitamin D deficiency are often too difficult to notice or appear too late.

Thanks to the rapid vitamin D tests, anyone can easily check their vitamin D level at home. Taking urgent measures in case of deficiency is essential for preventing potentially serious health problems.

Why is vitamin D testing important?

Vitamin D deficiency has been linked to some serious diseases such as osteoporosis, osteomalacia, multiple sclerosis, cardiovascular disease, pregnancy complications, diabetes, depression, stroke, autoimmune diseases, influenza, various types of cancer, infectious diseases, Alzheimer’s disease, obesity, high mortality, etc.

Some of the symptoms of vitamin D deficiency include fatigue, bone pain, muscle weakness, mood changes, frequent illness, and hair loss.

Taking vitamin D supplements is not recommended before checking your vitamin D level and consulting a medical practitioner who can advise you on the next steps. At the same time, a lack of symptoms does not necessarily mean that your vitamin D level is sufficient.

How do vitamin D tests work?

The organism is able to obtain vitamin D mainly through sunlight and to a lesser extent, through food. Once in the body, vitamin D is transported to the liver where it is metabolised to 25-hydroxyvitamin D. In medicine, this specific form of the vitamin is used to determine the concentration of vitamin D in the blood. The 25-hydroxyvitamin D level is considered the best indicator of vitamin D status.

To read the results, the test line (T) and control line (C) of the test cassette are used. The higher the concentration of 25-hydroxyvitamin D in the blood sample, the lighter the test line (T) will appear. The results are interpreted according to the colour card provided in the kit.

A coloured line will always appear in the control region (C), indicating that an appropriate volume of the sample has been added and the test procedure has been performed correctly.

How to interpret the results

One can talk about vitamin D deficiency when the level is lower than 10 ng/mL (or 25 nmol/L). When the level is between 10-30 ng/mL (or 25-75 nmol/L), this is considered insufficient. In both cases, it is recommended to review the results with a doctor who will advise you on the next steps.

The normal concentration of vitamin D in the blood usually ranges between 30-100 ng/mL (or 75-250 nmol/L).

When taking vitamin D supplements without a prescription from a medical professional, the level of the vitamin in the blood may reach values in excess. In this case, your doctor will assess your condition and decide whether you need to stop taking supplements. The good news is that when you’re obtaining the vitamin naturally through exposure to the sunlight or eating certain foods, it’s almost impossible to reach abnormally high levels of vitamin D.



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