At DeanSilverMD.com, we often hear from patients who feel persistently tired, mentally drained, or physically run down—despite eating clean, sleeping well, and staying active. The problem isn’t always stress or overexertion. In many cases, it’s something less obvious but deeply impactful: vitamin D deficiency.
Vitamin D, often referred to as the “sunshine vitamin,” is not just a simple nutrient. It functions more like a hormone, interacting with over 200 genes in the body and influencing everything from bone metabolism and immune health to inflammation and brain chemistry. While many people assume they’re getting enough from sunlight or diet, the reality is that vitamin D deficiency is now considered a global health epidemic. More than 42% of American adults are estimated to be deficient. In certain populations, such as individuals with darker skin or limited sun exposure, the rate is even higher.
At our integrative practice, we use comprehensive lab testing and metabolic screening to detect nutrient imbalances, including low vitamin D. But there are also signs your body gives you—early warnings that may be easy to overlook but are worth taking seriously. Let’s explore the most common symptoms of vitamin D deficiency and what to do if you suspect your levels are too low.
Chronic Fatigue That Doesn’t Resolve with Rest
One of the most reported—and most misunderstood—signs of vitamin D deficiency is unrelenting fatigue. This isn’t the typical tiredness that follows a poor night’s sleep. It’s the kind that lingers even after you’ve rested, and it often comes with brain fog, irritability, and a general lack of vitality. Clinical studies in both adults and children show a strong link between low vitamin D levels and reduced energy metabolism, poor sleep quality, and shorter sleep duration. Vitamin D plays a key role in mitochondrial function, which means that without it, your cells struggle to produce the energy you need to feel your best.
Lowered Immunity and Frequent Infections
Do you find yourself catching colds more often than usual? Are you recovering more slowly from the flu or respiratory infections? Vitamin D regulates the activity of immune cells, including T-cells and macrophages, which help your body fight off pathogens. Research confirms that people with low vitamin D levels are more susceptible to common respiratory illnesses, as well as viral infections like influenza and COVID-19. In our clinical experience, replenishing vitamin D can help restore immune resilience, especially during the winter months or in individuals with chronic inflammation.
Bone Discomfort and Musculoskeletal Pain
Vitamin D is critical for calcium absorption and bone mineralization. Without it, bones can become soft, brittle, or painful—a condition known as osteomalacia in adults. If you’re experiencing unexplained back pain, aching in your hips, or a dull, deep discomfort in your limbs, low vitamin D could be part of the equation. One review of 81 studies found a consistent link between musculoskeletal pain and vitamin D deficiency. Even when there’s no overt bone disease, the pain pathways in the body may be sensitized due to inadequate vitamin D levels.
Anxiety, Depression, and Emotional Instability
Vitamin D receptors are located throughout the brain, including areas associated with mood regulation. Multiple clinical reviews have associated low vitamin D levels with depressive symptoms, particularly in older adults and those with seasonal affective disorder. At DeanSilverMD.com, we take a root-cause approach to mental health and often find that correcting nutritional deficiencies—including vitamin D—can lead to significant improvements in mood, focus, and emotional balance. While vitamin D is not a substitute for mental health therapy, it can be a vital co-factor in your recovery plan.
Slower Wound Healing and Higher Inflammation
Your skin is your first line of defense, and vitamin D is a key player in skin repair and regeneration. If your wounds, scrapes, or surgical incisions are taking longer than normal to heal, it may be a sign of deficiency. Clinical studies show that vitamin D increases the production of growth factors essential for tissue healing. In diabetic patients, supplementation has been associated with accelerated healing of foot ulcers and reduced levels of inflammatory markers. For patients undergoing surgery or recovering from injury, we routinely evaluate and correct vitamin D status as part of the healing protocol.
Hair Thinning and Excessive Shedding
Hair loss, especially in women, can often be traced back to nutrient deficiencies. Among the most common is vitamin D. Recent studies suggest a link between low vitamin D and alopecia areata—an autoimmune condition that results in patchy hair loss—as well as diffuse thinning due to hormonal or inflammatory triggers. While hair loss can be multifactorial, optimizing vitamin D is a low-risk, high-reward intervention that can support follicular health and scalp circulation.
Muscle Weakness and Decreased Physical Performance
Vitamin D deficiency doesn’t just impact your bones—it also affects your muscles. The vitamin D receptor is expressed in muscle tissue, where it helps regulate strength, coordination, and repair. In both young athletes and older adults, low vitamin D has been shown to impair physical performance, reduce endurance, and increase fall risk. If you’ve noticed a sudden drop in your stamina, strength, or ability to recover from workouts, it may be time to get your levels checked.
Unexplained Weight Gain or Difficulty Losing Fat
There is emerging evidence linking vitamin D deficiency with increased body fat, especially in the abdominal region. While more research is needed, some studies suggest that low vitamin D may influence insulin resistance, appetite regulation, and fat storage. At our practice, we often see that patients with persistent weight struggles—despite a healthy diet and regular exercise—experience breakthroughs when we address underlying deficiencies.
Who Is Most at Risk for Deficiency?
Several factors can increase your likelihood of developing a deficiency. These include darker skin pigmentation, older age, living in northern latitudes, obesity, limited sun exposure, digestive issues (such as celiac or Crohn’s disease), kidney or liver dysfunction, and certain medications like steroids or statins. Even if you feel healthy, you may still be deficient—especially if your lifestyle limits your ability to synthesize vitamin D from sunlight.
How to Safely Restore Vitamin D Levels
The first step is testing. A simple 25-hydroxy vitamin D blood test can determine your current level. If you're below 30 ng/mL, your healthcare provider may recommend supplementation. For most adults, 1,500–2,000 IU of vitamin D3 daily is safe and effective, but higher doses may be required for those with severe deficiency. Magnesium is also essential, as it helps activate vitamin D. Be sure to support your body with foods like salmon, sardines, egg yolks, fortified milk, mushrooms, and leafy greens—or discuss a supplement plan tailored to your needs.
When to Seek Medical Support
If you’re experiencing any of the symptoms above—especially fatigue, frequent illness, emotional changes, or musculoskeletal pain—don’t wait for things to get worse. A functional wellness consultation can uncover the root cause and guide a comprehensive plan that restores nutrient balance, supports your metabolism, and enhances your long-term vitality.
Conclusion from DeanSilverMD.com
Fatigue isn’t always just stress or aging. Sometimes, it’s your body’s way of signaling a deeper imbalance. Vitamin D deficiency is one of the most common, yet underdiagnosed, contributors to poor health. The good news is that it’s completely reversible with the right approach. By identifying the warning signs early and supporting your body with personalized care, you can reclaim your energy, mood, and physical strength—naturally.