5 Reasons to Track Your Vitamin D Biomarker

The Biomarker Handbook is a curated series that seeks to provide readers with insights on each biomarker we cover in our blood test packages and its relation to our body.

In order to stay healthy and prevent a number of diseases and health conditions we need to consume sufficient amounts of different macro and micronutrients. The latter refers to nutrients our body requires in relatively small amounts such as vitamins and minerals. Abnormal levels of vitamins are a common occurrence and they always carry certain health consequences.

Definition of Vitamin D

Vitamin D or the ‘sunshine’ vitamin is a complex micronutrient. Despite its name, vitamin D is a pro-hormone. This is because vitamins cannot be produced by the body, and we need to consume them through our diets. On the other hand, when sunlight reaches the skin our body can synthesize vitamin D. Although it’s technically pro-hormone, vitamin D is classified as a fat-soluble vitamin naturally present in a very few foods, added to others, and produced by our body. An important function of vitamin D is to promote absorption of calcium in the gut and maintain adequate concentrations of both calcium and phosphate. The micronutrient is also required for bone growth, modulation of cell growth, reduction of inflammation, and neuromuscular and immune function. Normal levels of vitamin D are between 50nmol/l (20ng/ml) and 125 nmol/l (50ng/ml).

Importance of Tracking Vitamin D

We get vitamin D through our diet as well as through sun exposure. Estimates show that sun exposure on bare skin two to three times per week for 5-10 minutes can produce sufficient amounts of vitamin D. Since this micronutrient breaks down quickly, the stores can easily decrease, especially during winter. Before the body can use vitamin D, it needs to go through several processes. The very first transformation takes place in your liver where body converts vitamin D to a chemical called calcidiol or 25-hydroxyvitamin D.

Tracking vitamin D levels is important mainly because unlike other micronutrients, this vitamin isn’t found in many foods. As a result, it is easy to become deficient. Some people may also have excessive levels of vitamin D in the body due to uncontrollable supplementation. Testing vitamin D levels is also recommended for adults and children with weak bones, older adults, babies who were breastfed only, obese individuals, and to patients prior to their start with treatment for osteoporosis. People with kidney disease also should check their vitamin D levels.

Your doctor will tell you not to eat anything between four and eight hours before the 25-hydroxyvitamin D test is performed. It is a “regular” blood test where a lab technician or your doctor draws blood from a vein.

Signs and Symptoms to Watch Out For

Some people are deficient in vitamin D while others have excessive levels of this micronutrient. Both hypo- and hypervitaminosis D are characterized by different signs and symptoms that tell you something is wrong.

Symptoms of vitamin D deficiency are:

  • Back and bone pain
  • Bone loss
  • Depression
  • Fatigue
  • Hair loss
  • Muscle pain
  • Slow wound healing
  • Weakened immune system

Signs and symptoms of excessive levels of vitamin D are:

  • Constipation
  • Dehydration
  • Disorientation and confusion
  • Dizziness
  • Excessive thirst
  • Excessive urination
  • Fatigue
  • Heart arrhythmia
  • Hypertension (high blood pressure)
  • Loss of appetite and weight loss
  • Muscle weakness
  • Nausea and vomiting
  • Nervousness and irritability
  • Tinnitus (ringing in the ear)

Consequences of Having Abnormal Vitamin D Levels

If 25-hydroxyvitamin D test shows a ratio less than 30nmol/l (12ng/ml) it means a patient has vitamin D deficiency. Results showing values between 30nmol/l and 50nmol/l (20ng/ml) indicate potential vitamin D deficiency. On the other hand, values higher than 125nmol/l (50ng/ml) are considered too high and indicate a person has excessive vitamin D levels in the body. Hypo- and hypervitaminosis D carry a number of health consequences which only emphasize the importance of testing and checking the concentration of this micronutrient.

Vitamin D deficiency

Insufficient levels of vitamin D are caused by several factors including insufficient exposure to the sun, darker skin, obesity, malabsorption syndromes such as Crohn’s disease, and inadequate intake of vitamin D. This problem is very common. Figures show that about 41.6% of the US population is deficient in the sunshine vitamin.

Consequences associated with a deficiency in this micronutrient are:

  • Obesity – people with obesity-associated gene variants are more likely to have low vitamin D. Obesity increases the risk of heart disease, premature death, and different cancers
  • Diabetes – low vitamin D status contributes to insulin resistance
  • Hypertension – vitamin D indirectly modulates blood pressure and deficiency in this micronutrient may contribute to hypertension, which increases the risk of cardiovascular events such as heart attack and stroke
  • Fibromyalgia – a condition indicated by widespread musculoskeletal pain followed by sleep, fatigue, mood issues, and memory problems. It is estimated that 10 million Americans and 3% to 6% of world population have fibromyalgia. Low vitamin D levels increase inflammation which aggravates symptoms of this condition
  • Chronic fatigue syndrome – a disorder characterized by extreme tiredness and fatigue that doesn’t go away even after a patient gets enough sleep. Vitamin D plays a role in the strength of your muscles, joints, and bones which explains why deficiency makes you feel tired
  • Osteoporosis – a condition which occurs when the body loses too much bone, produces too little bone, or a combination of the two. As a result, bones become weak, brittle, and break easily. Numbers show that 200 million women worldwide have osteoporosis. About 1 in 3 women older than 50 experience osteoporotic fractures. Vitamin D deficiency impairs absorption of calcium and makes your bones vulnerable

Hypervitaminosis D

Excessive vitamin D is a rare, but potentially serious condition. Hypervitaminosis D isn’t caused by diet or sun exposure, but by excessive consumption of vitamin D supplements. Elevated levels of the vitamin are also caused by long-term estrogen therapy, antacids, isoniazid. The primary consequence of hypervitaminosis D is hypercalcemia or an accumulation of calcium in your blood. Other consequences of high vitamin D include kidney disease, liver disease, tuberculosis, hyperparathyroidism (enlargement of one or more parathyroid glands), sarcoidosis (an inflammatory condition affecting lymph glands), and histoplasmosis (a type of lung infection).

Ways to Balance These Levels

As seen above, both low and high concentration of vitamin D can negatively affect your health and quality of life. What you can do is to balance levels of this micronutrient through a healthy lifestyle. If you have Vitamin D deficiency, start including more foods containing vitamin D and fortified foods into your diet and strive to spend more time outdoors. You also need to exercise regularly to lose weight and keep it in a healthy range. In cases of vitamin D deficiency, your doctor usually recommends taking vitamin D supplements.

On the other hand, persons with hypervitaminosis D will need to make some changes in their lifestyle too. For example, your doctor will recommend discontinuing use of supplements you’re taking and he/she may also suggest lowering calcium intake until vitamin D returns to a healthy range. Focus on spending more time outdoors and consuming vitamin D through diet.

When to See the Doctor?

You should see your healthcare provider if you experience bone, joint, and muscle pain for a prolonged period. People who deal with fatigue, dehydration, constipation and other symptoms mentioned above for a few weeks should also schedule an appointment to see their doctor. Of course, if you already have problems with your bones, parathyroid levels, and osteoporosis you need to see your doctor regularly and consult regarding 25-hydroxyvitamin D test.

Further Testing to Check for Ailments Related to Abnormal Vitamin D Levels

Further tests are always practical for men and women with abnormal vitamin D levels. These tests may include:

  • Blood calcium test
  • Parathyroid hormone level
  • Bone markers
  • Urinalysis for kidney disease
  • Imaging tests (X-ray, CT scan) for osteoporosis


Vitamin D is vital for our health and wellbeing, but abnormalities are very common. Deficiency is more prevalent than hypervitaminosis D. Bearing in mind that abnormal levels of vitamin D induce different side effects and are associated with various health complications, tracking the concentration of this micronutrient is vital, particularly for high-risk individuals.

If you want to find out more about Vitamin D and why you should be tracking it, take a look at our lifestyle article here!

Interested in other biomarkers? Check out the rest of The Biomarker Handbook.

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