Who Has a Vitamin D Deficiency? Identifying Your Risk Factors

January 10, 2026 •

5 min read

According to the National Institutes of Health, nearly one out of four people in the United States have vitamin D blood levels that are too low or inadequate. A vitamin D deficiency can impact your health in various ways, from weakened bones and muscles to an increased risk of infections. Understanding your personal risk factors is the first step toward prevention and treatment.

Quick Summary

Several factors increase the risk of vitamin D deficiency, including limited sun exposure, darker skin, and older age. Certain health conditions, obesity, and specific medications can also impair your body's ability to produce or absorb this essential nutrient. Identifying these risks helps determine if testing or supplementation is needed.

Key Points

Older Adults: Skin's vitamin D synthesis decreases with age, placing individuals over 65 at higher risk, especially those with limited mobility.
Dark Skin Pigmentation: Higher melanin content reduces the skin's ability to produce vitamin D from sunlight, requiring longer sun exposure.
Limited Sun Exposure: People who are homebound, work indoors, or live in northern latitudes often do not get enough sun to produce adequate vitamin D.
Obesity and Malabsorption: Excess body fat stores vitamin D, while conditions like Crohn's and celiac disease can prevent proper absorption.
Infants and Chronic Illness: Breastfed infants are at risk, and chronic kidney or liver disease can interfere with the body's use of vitamin D.
Common Symptoms: Signs can include fatigue, bone and muscle pain, a depressed mood, and frequent illnesses.
Prevention: Maintain healthy vitamin D levels through moderate sun exposure, a balanced diet with fortified foods, and appropriate supplementation under a doctor's guidance.

Who Is Most at Risk for Vitamin D Deficiency?

While anyone can experience a vitamin D deficiency, several populations face a significantly higher risk due to biological, environmental, and lifestyle factors. The primary source of vitamin D for most people comes from sun exposure, but diet and supplementation also play a role. When these sources are insufficient, deficiency can occur.

Populations with Increased Risk

Older Adults: The skin's ability to synthesize vitamin D from sunlight declines with age. Additionally, older adults often spend more time indoors and may have reduced dietary intake, further increasing their risk. Research indicates that older individuals, especially those in nursing homes, have a high prevalence of deficiency.
Individuals with Dark Skin: Melanin, the pigment that gives skin its color, acts as a natural sunscreen, reducing the skin's capacity to produce vitamin D from ultraviolet B (UVB) radiation. For this reason, individuals with darker skin tones require significantly more sun exposure to produce the same amount of vitamin D as those with lighter skin.
Breastfed Infants: Human breast milk naturally contains very little vitamin D. The American Academy of Pediatrics recommends that breastfed infants receive a daily vitamin D supplement of 400 IU starting shortly after birth. Infant formula, however, is fortified with vitamin D.
Individuals with Limited Sun Exposure: People who are homebound, have professions that restrict outdoor time, or live in high-latitude regions with reduced winter sunlight are at high risk. People who wear clothing that covers most of their body for cultural or religious reasons are also less likely to get sufficient sunlight. Consistent use of sunscreen can also limit vitamin D production.
People with Obesity: Individuals with a body mass index (BMI) of 30 or higher are associated with lower vitamin D levels. The excess body fat sequesters the fat-soluble vitamin D, preventing it from circulating in the blood. Higher doses of supplementation may be necessary for these individuals to reach normal levels.
Those with Malabsorption Conditions: Medical conditions that impair fat absorption in the intestines can also interfere with vitamin D absorption, as it is a fat-soluble vitamin. Examples include Crohn's disease, celiac disease, and cystic fibrosis. People who have undergone gastric bypass surgery are also at risk.
People with Liver or Kidney Disease: The liver and kidneys are essential for converting vitamin D into its active form that the body can use. Chronic liver or kidney disease can therefore hinder this process, leading to a deficiency.

Common Symptoms of a Vitamin D Deficiency

Symptoms of vitamin D deficiency can be subtle and may mimic other conditions, which is why a blood test is crucial for diagnosis. Signs to watch for include:

Fatigue and Weakness: Persistent feelings of tiredness, fatigue, and muscle weakness are common signs of deficiency.
Bone and Muscle Pain: Vitamin D is vital for bone and muscle health. Low levels can lead to aches, pains, and weakness in the muscles and bones.
Frequent Infections: The vitamin plays a role in immune function, and a deficiency can lead to increased susceptibility to infections.
Depressed Mood: Research has found a link between low vitamin D levels and a higher risk of depression.
Hair Loss: Some studies have identified a link between vitamin D deficiency and hair loss or alopecia.
Impaired Wound Healing: Slow wound healing is another potential symptom associated with low vitamin D.

Risk Factors vs. Healthy Practices for Vitamin D Status


Factor	High-Risk Group Profile	Healthy Practice Profile
Sunlight Exposure	Living in a high-latitude region, indoors most of the time, or consistent, complete skin coverage.	Regular, moderate sun exposure (e.g., 5–30 minutes) to arms, legs, and face.
Skin Pigmentation	Darker skin, which requires more sun exposure for vitamin D production.	Lighter skin, which produces vitamin D more efficiently from sunlight.
Age	Older adults (65+ years) due to decreased skin synthesis and reduced mobility.	Young and middle-aged adults, though deficiency is still possible without proper intake.
Body Weight	Obesity (BMI > 30), as body fat sequesters vitamin D.	Healthy weight range, which allows for better vitamin D bioavailability.
Dietary Intake	Diet with limited fortified foods or few natural vitamin D sources like fatty fish.	Includes fatty fish, fortified dairy, eggs, and cereals in diet.
Health Conditions	Chronic kidney or liver disease, Crohn's, celiac disease, cystic fibrosis.	No pre-existing conditions that affect vitamin D metabolism or absorption.
Medication Use	Taking certain anti-seizure drugs, steroids, or cholesterol-lowering medications.	Not taking medications that interfere with vitamin D metabolism.

Diagnosis and Prevention

For those with risk factors or symptoms, a blood test, specifically the 25-hydroxyvitamin D [25(OH)D] test, is the most accurate method for diagnosis. If a deficiency is confirmed, treatment typically involves supplementation to restore adequate levels.

Prevention focuses on ensuring sufficient vitamin D intake through a combination of methods:

Sensible Sun Exposure: Short, regular periods of sun exposure can help the body produce vitamin D. However, balance is key to avoid increasing the risk of skin cancer, and sunscreen use is still recommended for prolonged exposure.
Dietary Sources: Incorporating foods naturally rich in vitamin D, such as fatty fish like salmon and tuna, or fortified foods like milk, cereals, and orange juice, can boost intake.
Supplements: When sun exposure is limited or dietary intake is insufficient, supplements are a reliable way to maintain healthy vitamin D levels. The appropriate dose depends on individual needs and deficiency severity, so a healthcare provider should be consulted.

Conclusion

Millions of people worldwide, including many in the U.S., face the risk of vitamin D deficiency. Understanding who is most susceptible and recognizing the potential signs and symptoms are crucial for proactive health management. From infants and older adults to people with certain medical conditions, a variety of factors can inhibit the body's ability to get enough of this vital nutrient. Consulting with a healthcare provider for testing and discussing appropriate prevention strategies, such as supplements or diet changes, can help ensure healthy vitamin D levels and support overall well-being. A useful resource for dietary information can be found at the National Institutes of Health Office of Dietary Supplements.

Frequently Asked Questions

The most common causes of vitamin D deficiency are inadequate exposure to sunlight, as the body produces vitamin D in response to sun exposure, and insufficient dietary intake.

Yes, darker skin pigmentation reduces the skin's ability to produce vitamin D from sunlight. This is because melanin, the pigment responsible for skin color, acts as a natural sunblock. People with dark skin need more sun exposure than those with lighter skin to produce the same amount of vitamin D.

Older adults are at higher risk because their skin becomes less efficient at producing vitamin D from sunlight as they age. They also tend to spend more time indoors and may consume a diet lower in vitamin D.

Conditions that interfere with fat absorption, such as celiac disease, Crohn's disease, and cystic fibrosis, can cause deficiency. Chronic kidney and liver disease also affect the body's ability to convert vitamin D into its active form.

Yes, individuals with a BMI of 30 or higher are at a greater risk of deficiency. The vitamin D is stored in body fat, making it less available for use in the bloodstream. Higher doses of supplements may be needed to overcome this effect.

Common symptoms can include fatigue, bone and muscle pain, muscle weakness, frequent infections, hair loss, and a depressed mood. These symptoms can be mild and often overlooked.

Prevention involves a combination of strategies: getting moderate sun exposure, consuming foods rich in or fortified with vitamin D, and taking supplements if dietary and sun sources are insufficient. Consult a healthcare provider for personalized guidance.