Vitamin D and fatigue, is there a relationship?

Vitamin D and fatigue, is there a relationship?

Many researchers have been studying the link between fatigue and vitamin D deficiency. About 7% to 45% of people wor

Many researchers have been studying the link between fatigue and vitamin D deficiency. About 7% to 45% of people worldwide suffer from fatigue. They cannot perform daily activities in a good state, and they feel tiredness, irritability, sleepiness, headaches, and exhaustion. Scientists discovered that vitamin D deficiency is a possible reason for this state. Researchers in this study found that people who complained of fatigue have vitamin D deficiency. After giving them vitamin D therapy for five weeks, they felt an improvement. Let's dive in to know more details about the importance of vitamin D and how the deficiency can cause fatigue.

What is vitamin D?

Vitamin D is one of the fat-soluble vitamins that is known as Calciferol. You can get it from dietary supplements or some foods. Additionally, your body can synthesize vitamin D endogenously only when exposed to the sun's ultraviolet rays. It has two forms inside your body, calcidiol (25-hydroxyvitamin D [25(OH)D]) and calcitriol (1,25-dihydroxy vitamin D [1,25(OH)2D]). 

What are the functions of vitamin D?

  • Improve calcium absorption
  • Prevent osteomalacia (bone softening) and osteoporosis (weak bone) in adults, thus preventing fractures
  • Prevent rickets in children
  • Maintain optimal function of parathyroid glands
  • Keep your bones strong
  • Reduce body inflammation
  • Promote your immune system
  • Modulation of the following processes; cell growth, neuromuscular function, and glucose metabolism

What is vitamin D deficiency?

The usual range of vitamin D falls between 20 and 50 ng/mL. When your serum levels are down below 20 ng/ml, you have a deficiency. However, be cautious not to let your serum vitamin D levels be more than 50 ng/ml as you will have adverse effects. According to this study published in the European Journal of clinical nutrition, 7.4% of Canadians have severe vitamin D deficiency below 12 ng/ml. In comparison, 37% have serum vitamin D levels below 20 ng/ml. 

What are the signs of vitamin D deficiency?

  • Fatigue
  • Depression
  • Bone and muscle pain
  • Rickets in children that may cause hypocalcemic seizures, developmental delay, and dental abnormalities
  • Osteomalacia and osteoporosis in adults
  • High prevalence of infections due to weak immune system

How does vitamin D deficiency cause fatigue?

According to a study published in Medicine journal, how vitamin D deficiency causes fatigue is still unknown. However, some theories explain the mechanism:

  • The first is that vitamin D has many receptors in your brain and central nervous system to regulate dopaminergic neurons. Vitamin D deficiency causes dopamine imbalance leading to central fatigue. 
  • The second is that vitamin D has a critical role in brain serotonin synthesis. If there is a defect in this process, you may experience fatigue. 
  • The third is that researchers noticed that vitamin D therapy in deficient people resulted in muscle mitochondrial oxidative phosphorylation. This process could improve fatigue. 

What are the causes of vitamin D deficiency?

There are many reasons for vitamin D deficiency, including health conditions, medications, or dietary reasons. 

  • Health conditions: Many diseases prevent adequate vitamin D absorption from the intestine or prevent vitamin D activation inside the body. These conditions are lactose intolerance, cystic fibrosis, celiac disease, Crohn's disease, and liver and kidney illness. 
  • Medications: Medications that can lower vitamin D levels are laxatives, steroids, cholesterol-lowering drugs, weight loss drugs (orlistat), seizure-control drugs, and tuberculosis drugs (rifampin)
  • Weight loss surgeries: The patient can't consume enough nutritious food due to the small stomach size after the surgery. Moreover, the patient can't get enough nutrients and vitamins, so the doctor has to monitor the case to avoid complications regularly
  • Obesity: Obese people are more vulnerable to have vitamin D deficiency because the fat cells isolate vitamin D preventing it from releasing. Furthermore, obese people need higher doses of vitamin D than others with average weight. 
  • Dietary reasons: if you don't consume enough foods rich in vitamin D or are a vegan, you may experience a deficiency. 
  • Lack of sun exposure: when the sun's ultraviolet rays come in contact with your skin, they stimulate your body to synthesize vitamin D. 

Who are people at high risk of vitamin D deficiency?

  • Senior people: by age, your skin can't synthesize vitamin D efficiently. Additionally, seniors are more likely to stay home, so they can't get enough sun rays. 
  • Dark-colored skin: vitamin D synthesis in people with dark skin sounds challenging more than those with fair-colored skin. That is why they need to stay in a sunny area more than other people. 
  • Babies fed breast milk: breast milk does not have enough vitamin D, putting the baby at risk of deficiency if not fed additional formulas. 

How to determine vitamin D deficiency?

If you have any previous symptoms, you can see a physician and ask them to order a blood test. The only way to detect vitamin D status is by performing a 25-hydroxyvitamin D blood test. The result shows as follows, however, note that the numbers may differ a little between labs:

nmol/l ng/ml Health status
<30 <12 deficiency
30 to <50 12 to <20 inadequate
≥50 ≥20 normal

How to treat vitamin D deficiency?

The treatment includes consuming foods rich in vitamin D and taking a dietary supplement containing vitamin D. Additionally, do not forget to be exposed to the sun between 10 a.m. and 4 p.m for 15-20 minutes two or three days per week.

How to influence vitamin D absorption?

  • Wear fabrics and colors that allow UV radiations to strike your skin: Researchers in this study found that wearing lightweight, non-synthetic fibers, including cotton and linen, is better than wool, silk, nylon, and polyester. Moreover, white color clothes are better than black ones. 
  • Try maintain a healthy body weight: An excess of fat may prevent vitamin D from releasing and doing its functions so following a healthy diet will improve vitamin D absorption
  • Ensure you have normal calcium and magnesium levels: Your body won't absorb vitamin D efficiently if you have calcium and magnesium deficiency. That is why you have to receive treatment for magnesium and calcium deficiency along with vitamin D. 
  • Consume vitamin D treatment following a fatty meal: Vitamin D is a fat-soluble vitamin that is absorbed efficiently in the presence of healthy fats, including salmon or nuts. 

What are foods that are high in vitamin D?

Besides sun rays and dietary supplements, there are some foods, however not many, that contain vitamin D, including 

  • Fatty fish
  • Some fish-liver oils
  • Mushrooms
  • Eggs from hens fed vitamin D
  • Beef liver
  • Cheddar cheese
  • Chicken breast
  • Foods fortified with vitamin D

How much is vitamin D recommended to prevent fatigue?

The following table displays how many micrograms you need daily from vitamin D depending on every age

Age Recommended daily allowance
0-12 months 10 mcg
1-13 years 15 mcg
14-18 years 15 mcg
19-50 years 15 mcg
51-70 years 15 mcg
>70 years 20 mcg


Vitamin D and fatigue are well related. If you experience fatigue that has no medical reason for a particular health condition, go to a physician to do a vitamin D test as you possibly have a deficiency. Consume your vitamin D pills regularly and go out for sun exposure to get enough vitamin D. Finally, ensure your weight is ideal and incorporate foods rich in vitamin D into your meals.

This article offers general information only and is not intended as medical or other professional advice. A healthcare provider should be consulted regarding your specific situation. While the information presented is believed to be factual and current, its accuracy is not guaranteed and it should not be regarded as a complete analysis of the subjects discussed. All expressions of opinion reflect the judgment of the authors as of the date of publication and are subject to change. No endorsement of any third parties or their advice, opinions, information, products or services is expressly given or implied by Mednow or its affiliates.


Get Started

We recommend

Ozempic and Beyond: Exploring the Benefits and Uses of GLP1 Receptor Agonists

Type 2 diabetes is a chronic condition that affects millions of people worldwide. There's no cure for type 2 diabetes.

The Importance of Medication Adherence in Overall Health

Canadians have vastly improved their health and quality of life thanks to modernmedical advancements and medications.

Why digitally enabled pharmacy is a key part of healthcare’s future

The healthcare industry is rapidly evolving, and digital technology is playing a crucial role in this transformation.