Vitamin D Deficiency

Fatigue, muscle weakness, and bone pain can have many causes. In some cases, vitamin D deficiency may be contributing to the problem.

Vitamin D helps the body absorb calcium and maintain healthy bones, but its role goes beyond bone health. It also supports muscle function and helps regulate important processes throughout the body.

Vitamin D plays an important role in bone health, calcium balance, and metabolism. That’s why doctors often evaluate vitamin D levels in people with osteoporosis, parathyroid disorders, and other endocrine conditions.

Although vitamin D is often called a vitamin, it acts more like a hormone once it’s activated in the body. It helps regulate calcium levels and supports many important biological processes.

Vitamin D deficiency often comes up in endocrine care because many hormone-related conditions affect bone health, calcium balance, and metabolism.

Low vitamin D levels may be seen in people with:

• Osteoporosis
• Osteopenia
• Parathyroid disorders
• Certain metabolic conditions
• Obesity
• Hormone-related bone loss

Because vitamin D and calcium work closely together, vitamin D levels often play a role in diagnosing and managing certain endocrine conditions.

Vitamin D deficiency occurs when the body doesn’t have enough vitamin D to support normal biological functions. Low levels are common and may develop gradually over time.

Some people have no symptoms at first. Others begin to notice changes as vitamin D levels continue to decline.

Vitamin D helps the body absorb calcium and maintain healthy bones and muscles. When levels are too low, the body may struggle to absorb enough calcium from food and begin drawing calcium from the bones.

Vitamin D deficiency may contribute to:

• Bone thinning
• Increased fracture risk
• Muscle weakness
• Skeletal discomfort

People with vitamin D deficiency may also experience:

• Fatigue or low energy
• Muscle aches
• Bone pain
• Difficulty with balance
• Increased falls, especially in older adults
• Stress fractures
• Worsening bone loss

Severe deficiency can lead to osteomalacia, a condition that causes soft bones in adults. In children, severe deficiency can cause nutritional rickets, which affects bone development.

Vitamin D deficiency can occur for several reasons. Some people don’t get enough vitamin D through sunlight exposure or diet. Others have medical conditions that affect how vitamin D is absorbed or processed.

Risk factors include:

• Limited sun exposure
• Older age
• Osteoporosis
• High body weight
• Malabsorption disorders
• Chronic kidney disease
• Certain medications
• Diets low in vitamin D-rich foods

Vitamin D deficiency is typically diagnosed with a blood test called 25-hydroxyvitamin D, or 25(OH)D.

Not everyone needs routine vitamin D screening. Testing is usually recommended based on:

• Symptoms
• Medical history
• Bone health concerns
• Individual risk factors

Your doctor will determine whether testing is appropriate based on your overall health and medical history.

Treatment is about more than simply raising vitamin D levels. It also helps support healthy bones, calcium balance, and metabolic health.

Treatment may include:

• Vitamin D supplementation
• Dietary changes
• Monitoring vitamin D levels
• Management of underlying medical conditions

Some people may require higher-dose vitamin D replacement under medical supervision.

Vitamin D comes from three primary sources:

• Sunlight exposure
• Food
• Supplements

When your skin is exposed to sunlight, your body can produce vitamin D naturally. But vitamin D production varies based on factors such as:

• Geographic location
• Season
• Age
• Skin tone
• Sunscreen use
• Time spent outdoors

Sunlight can help your body make vitamin D, but it’s not always enough. Some people may still need vitamin D from food or supplements.

Foods that contain vitamin D include:

• Fatty fish
• Egg yolks
• Fortified dairy products
• Fortified cereals

Routine vitamin D testing is not recommended for every healthy adult. However, testing may be appropriate for people with:

• Osteoporosis or recurrent fractures
• Parathyroid disorders
• Malabsorption conditions
• Chronic kidney disease
• Long-term steroid use
• Symptoms of vitamin D deficiency
• Certain metabolic or endocrine conditions

Fatigue, muscle weakness, bone pain, and recurrent fractures can have many causes. Vitamin D deficiency may be one of them.

If you’re concerned about vitamin D deficiency, osteoporosis, calcium balance, or a related endocrine condition, schedule an appointment with our San Antonio endocrinology team. We can evaluate your symptoms, review your risk factors, and determine whether testing or treatment may be appropriate.

1. What is the difference between vitamin D2 and vitamin D3?

Vitamin D2 comes from plant sources, while vitamin D3 comes from animal sources and is also the form your body produces after sunlight exposure. Research suggests vitamin D3 may be more effective at raising and maintaining vitamin D levels.

2. Can I get enough vitamin D from sunlight alone?

It depends. Vitamin D production varies based on where you live, the time of year, sunscreen use, skin tone, and how much time you spend outdoors. Some people may still need vitamin D from food or supplements.

3. Should I take high-dose vitamin D supplements?

Not necessarily. More vitamin D is not always better. The appropriate dose depends on your age, medical history, medications, diet, and current vitamin D levels. Your doctor can recommend the amount that is right for you.

4. Can vitamin D deficiency cause fatigue?

Yes. Fatigue and low energy are common symptoms of vitamin D deficiency. Fatigue can have many causes. Testing can help determine whether vitamin D deficiency may be contributing to your symptoms.