Vitamin D—often called the “sunshine vitamin”—plays a critical role in everything from bone strength to immune health and mood regulation. Yet despite its importance, vitamin D deficiency is surprisingly common. According to Dr. Pedi Mirdamadi, ND, many people assume spending time outdoors is enough to maintain healthy levels, but that’s not always the case.
In a recent TikTok, Dr. Mirdamadi explained that even people who are regularly exposed to sunlight can still test low in vitamin D due to factors like genetics, geography, altitude, skin pigmentation, age, and how efficiently the body converts sunlight into usable vitamin D. He notes that he even tests surfers—people who spend hours in the sun—whose levels are often “very, very low.”
Here are six common signs your body may be deficient in vitamin D, according to Dr. Mirdamadi and additional health research.
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1. Persistent Fatigue and Low Energy
Feeling exhausted even after a full night’s sleep? Dr. Mirdamadi says fatigue is one of the earliest and most overlooked signs of low vitamin D. This nutrient is essential for muscle function, cellular energy production, and overall strength. When levels drop, many people report feeling sluggish, weak, or chronically tired without an obvious reason.
2. Frequent Colds, Infections, or Slow Recovery
If you’re constantly catching colds or feel like you take longer than usual to recover, vitamin D may be playing a role. According to Dr. Mirdamadi, vitamin D is “crucial for a healthy immune system.” Low levels can weaken immune defenses, making the body more susceptible to infections and inflammation.
3. Anxiety, Low Mood, or Depression
Mental health challenges such as anxiety or depression can also be linked to vitamin D deficiency. Dr. Mirdamadi explains that vitamin D is involved in the synthesis of neurotransmitters that regulate mood. Low levels have been associated with increased rates of depressive symptoms, seasonal affective disorder, and heightened anxiety.
4. Weak Bones, Bone Pain, or Osteoporosis
Vitamin D is essential for calcium absorption and bone remodeling. Without enough of it, bones can become weak, brittle, or painful over time. Dr. Mirdamadi highlights osteoporosis as a key red flag, especially for older adults, but bone pain and fractures can occur at any age when deficiency is severe.
5. Muscle Weakness or Aches
Beyond bones, vitamin D is vital for muscle function. Low levels may cause muscle soreness, cramps, or weakness, particularly in the legs and lower back. Some people mistake this for aging, overexertion, or poor posture when it may actually stem from a nutrient deficiency.
6. Hair Thinning or Increased Hair Shedding
Emerging research suggests vitamin D plays a role in hair follicle cycling. Low levels have been linked to hair thinning and excessive shedding in some individuals, especially women. While hair loss is multifactorial, vitamin D deficiency may be a contributing factor worth investigating.
The Bottom Line
Vitamin D deficiency can show up in subtle ways long before serious health issues develop. Dr. Mirdamadi advises his patients to have their vitamin D levels checked at least once a year, especially if they experience ongoing fatigue, frequent illness, mood changes, or bone discomfort.
Because sun exposure alone often isn’t enough, testing is the only reliable way to know where your levels stand.
If results are low, a healthcare provider can recommend dietary changes, safe supplementation, or lifestyle adjustments tailored to your needs. If you’ve been feeling “off” and can’t pinpoint why, vitamin D might be a good place to start.
