Research shows that 30% to over 90% of healthcare workers have vitamin D deficiency depending on their location and job type, with nurses and night-shift workers most affected. According to Gram Research analysis of 36 studies from 2010-2025, this happens because healthcare workers spend long hours indoors under artificial lights and have limited sun exposure. The good news: studies demonstrate that vitamin D supplements, especially at higher doses, effectively raise blood levels and reduce respiratory infections among healthcare workers.
A major review of 36 studies from 2010-2025 found that healthcare workers like doctors, nurses, and hospital staff have surprisingly high rates of vitamin D deficiency—sometimes affecting up to 90% of workers in certain areas. According to Gram Research analysis, this happens because healthcare workers spend long hours indoors, work night shifts, and get limited sun exposure. The research shows that low vitamin D levels may weaken their immune systems, cause muscle and bone problems, and even affect how much work they can accomplish. The good news: studies show that vitamin D supplements, especially at higher doses, can improve their levels and reduce respiratory infections.
Key Statistics
A 2026 scoping review of 36 studies found that vitamin D deficiency affects 30% to over 90% of healthcare workers worldwide, with prevalence varying by geographic region, season, and job type, particularly among nurses and shift workers.
According to research reviewed by Gram, randomized controlled trials demonstrated that high-dose vitamin D supplementation improved serum vitamin D levels and reduced respiratory infections among healthcare workers.
A 2026 analysis of published literature identified that indoor work, long shifts, night duties, limited sun exposure, female sex, younger age, and higher body mass index are key determinants of vitamin D deficiency in healthcare workers.
Research from 2010-2025 shows that vitamin D deficiency in healthcare workers is linked to immune vulnerability, including higher rates of SARS-CoV-2 infection and musculoskeletal issues, with limited evidence suggesting higher vitamin D levels may reduce work absenteeism.
The Quick Take
- What they studied: Whether healthcare workers have low vitamin D levels and how this affects their health and ability to work
- Who participated: 36 different studies involving doctors, nurses, hospital staff, and other healthcare workers from around the world between 2010 and 2025
- Key finding: Between 30% to over 90% of healthcare workers have vitamin D deficiency depending on where they live and their job type, with nurses and night-shift workers most affected
- What it means for you: If you work in healthcare, you’re at higher risk for low vitamin D. Getting your levels checked and taking supplements may help you feel better, get sick less often, and be more productive at work—but talk to your doctor first
The Research Details
Researchers looked at 36 published studies from 2010 to 2025 about vitamin D levels in healthcare workers. They searched two major medical databases (PubMed and Scopus) for studies that measured vitamin D in the blood and tracked health or work outcomes. Most studies (30) were cross-sectional, meaning they took a snapshot of workers at one point in time. Two studies followed workers over time to see what happened, and four studies tested whether giving vitamin D supplements actually helped—including two gold-standard randomized controlled trials where some workers got supplements and others got placebos.
The researchers were careful to only include studies that clearly defined healthcare workers according to the World Health Organization’s definition and actually measured vitamin D in blood samples. This approach, called a scoping review, helps summarize what we know across many different studies and identify gaps in our knowledge.
This type of review is important because it pulls together evidence from many different places and populations, giving us a bigger picture than any single study could provide. It helps doctors and public health officials understand whether this is a real problem worth addressing.
Healthcare workers are essential to keeping everyone healthy, but they can’t do their jobs well if they’re not healthy themselves. By reviewing all available research together, scientists can identify patterns that might not be obvious in single studies. This helps us understand whether low vitamin D is just a coincidence or a real occupational health problem that needs solutions.
This review followed strict international guidelines (PRISMA-ScR) for how to conduct and report systematic reviews, which makes it more reliable. However, the studies included varied widely in how they measured vitamin D, what they considered ‘deficiency,’ and where they were conducted, which makes it harder to compare results directly. The fact that most studies were cross-sectional (snapshots in time) rather than long-term studies means we can’t always prove that low vitamin D causes health problems—only that they occur together.
What the Results Show
The review found that vitamin D deficiency is extremely common among healthcare workers worldwide, but the rates vary dramatically. In some regions and seasons, more than 90% of workers had low levels, while in others it was around 30%. The variation depends on geography (how far north or south you live), season (winter versus summer), and job type.
Nurses and shift workers—especially those working night shifts—had the highest rates of deficiency. This makes sense because these workers spend the most time indoors under artificial lights and have the least predictable schedules for getting outside. Other risk factors included working long shifts, female sex, younger age, higher body weight, and religious or cultural clothing that covers the skin.
When researchers looked at health effects, they found that workers with low vitamin D had weaker immune systems and got respiratory infections more often. Some studies suggested links to muscle and bone pain, though the evidence was less consistent. A few studies hinted that workers with better vitamin D levels might miss fewer days of work due to illness, though more research is needed to confirm this.
The most encouraging finding came from intervention studies: when healthcare workers took high-dose vitamin D supplements, their blood levels improved significantly and they had fewer respiratory infections. Two randomized controlled trials—the gold standard of research—confirmed that supplementation worked.
The review confirmed that vitamin D levels change with the seasons, being lower in winter and higher in summer, which is expected since sun exposure is the main way our bodies make vitamin D. Some studies suggested links between low vitamin D and depression or anxiety among healthcare workers, but the evidence was mixed and not as clear as the immune system findings. The research also highlighted that different labs use different methods to measure vitamin D, which can make it hard to compare studies and determine what counts as ‘deficiency.’
This review updates and expands on previous research by including studies through 2025 and focusing specifically on healthcare workers. Earlier research had shown vitamin D deficiency is common in many professions, but this review confirms it’s particularly prevalent in healthcare settings. The findings align with what we know about vitamin D’s role in immune function and respiratory health from general population studies, but highlight that healthcare workers face unique occupational risk factors.
The biggest limitation is that most studies were cross-sectional snapshots rather than long-term follow-ups, so we can’t definitively say that low vitamin D causes health problems—only that they occur together. The studies used different definitions of deficiency and different measurement methods, making direct comparisons difficult. Very few studies actually tested whether vitamin D supplements improved work productivity or reduced sick days, so that connection is still unclear. The review also couldn’t determine exact sample sizes across all studies, and most research came from specific regions, so results may not apply everywhere equally.
The Bottom Line
Healthcare workers should get their vitamin D levels checked, especially if they work night shifts, spend most time indoors, or live in northern climates. If levels are low, supplementation appears effective—studies show high-dose supplements improved blood levels and reduced respiratory infections. Start with 1,000-2,000 IU daily, but ask your doctor for the right dose for you. Moderate confidence: the evidence for supplements improving health is strong, but evidence for improving work productivity is still limited.
Healthcare workers (doctors, nurses, hospital staff, therapists) should especially pay attention, particularly those working night shifts or long indoor hours. Anyone with limited sun exposure, darker skin tone, or religious/cultural clothing that covers skin should also consider checking their vitamin D. This is less critical for people who get regular outdoor sun exposure and eat vitamin D-rich foods.
Blood vitamin D levels typically improve within 4-8 weeks of starting supplements. Immune system benefits and reduced infection rates may take 2-3 months to become noticeable. Improvements in energy, mood, or work performance could take longer and vary by individual.
Frequently Asked Questions
Do healthcare workers have more vitamin D deficiency than other people?
Yes, research shows healthcare workers have significantly higher rates of vitamin D deficiency—up to 90% in some regions—compared to general populations. This is primarily due to spending long hours indoors, working night shifts, and having limited sun exposure during their work schedules.
Can vitamin D supplements help healthcare workers get sick less often?
Research suggests yes. Randomized controlled trials found that high-dose vitamin D supplementation reduced respiratory infections among healthcare workers. However, more studies are needed to confirm benefits for other types of illness and overall work productivity.
What causes vitamin D deficiency in nurses and doctors?
Multiple factors contribute: spending most of the day indoors under artificial lights, working night shifts with reversed sleep schedules, limited outdoor time, geographic location, season, and individual factors like skin tone, age, and body weight. Lack of supplementation also plays a role.
How much vitamin D should healthcare workers take as a supplement?
Studies showing benefits used high-dose supplementation, typically 1,000-2,000 IU daily or higher, but the optimal dose varies by individual. Consult your doctor to determine the right dose based on your blood vitamin D level and personal health factors.
Does low vitamin D affect how much work healthcare workers can do?
Limited evidence suggests higher vitamin D levels may reduce presenteeism (working while sick), but more research is needed to confirm this connection. Low vitamin D is clearly linked to immune weakness and infections, which can impact work performance indirectly.
Want to Apply This Research?
- Log your vitamin D supplement intake daily and track respiratory infections or sick days monthly. Note any changes in energy levels, muscle soreness, or mood every two weeks to identify patterns.
- Set a daily reminder to take your vitamin D supplement at the same time each day (ideally with a meal for better absorption). If you work indoors, schedule 15-20 minutes of outdoor time during breaks when possible, especially during lunch hours.
- Get blood vitamin D levels tested every 3 months initially to confirm supplementation is working, then annually once stable. Track seasonal patterns—you may need higher doses in winter months. Monitor for improvements in illness frequency, energy, and work attendance over 6-month periods.
This article summarizes research findings and should not replace professional medical advice. Healthcare workers concerned about vitamin D deficiency should consult their physician for blood testing and personalized supplementation recommendations. Vitamin D supplementation may interact with certain medications or conditions. Always discuss any new supplement regimen with your healthcare provider before starting. This review identifies evidence gaps, and individual results may vary based on personal health status, geographic location, and other factors.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.