A 30-year-old professional said he had hit a brick wall. “My personal energy has tanked, I am chronically exhausted. I cannot recall discussions, details and decisions from the day before. I tried everything. I ate better. Slept earlier. Walked. Watched motivational videos. Read inspiring stories. Nothing worked,” he told me.
This is a story many people quietly relate to. The constant tiredness. The lack of drive. The feeling that even simple tasks take effort. It is easy to blame stress, poor sleep or a busy lifestyle. But in some cases, the cause is something far more basic and often overlooked, even when we do the usual package of tests: Vitamin D deficiency.
More than a bone vitamin
Vitamin D is commonly associated with bone health. Most of us know it helps the body absorb calcium and keeps bones strong. What many people do not realise is that vitamin D also plays a role in muscle strength, immune function and even mood regulation.
When levels drop, the symptoms are not always dramatic. They can be subtle and confusing.
Unusual and often ignored signs
One of the most common yet misunderstood signs is ongoing tiredness. This is not just feeling sleepy after a long day. It is a deep, lingering fatigue that does not improve with rest. People often describe it as feeling drained even after a full night’s sleep. Vitamin D receptors are present in many tissues of the body, including muscles and the brain. Low levels can affect energy production and overall physical performance, leading to constant exhaustion.
A feeling of hopelessness, irritability or reduced interest in daily activities can sometimes be linked to low vitamin D. Research suggests that vitamin D influences the production of certain brain chemicals involved in mood regulation. When someone feels unmotivated despite trying lifestyle changes, it may not be a matter of willpower. It may be a biological imbalance.
Muscle weakness or body aches
Unexplained muscle weakness, back pain, or general body aches can be early warning signs. Vitamin D helps maintain muscle function. Deficiency can cause subtle weakness that makes routine tasks feel harder than usual.
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Some people report difficulty climbing stairs, getting up from a seated position, or feeling sore without any clear reason.
Since Vitamin D supports the immune system, low levels may make a person more prone to colds, respiratory infections or slow recovery from illness. If someone finds themselves falling sick more often than usual, it is worth getting tested for deficiencies.
Brain fog, difficulty focussing or forgetfulness can also be associated with low vitamin D. While these symptoms are non-specific and can have many causes, they should not be ignored when seen along with fatigue and low mood.
Who is at risk?
Vitamin D is often called the “sunshine vitamin” because the body produces it when the skin is exposed to sunlight. People who work indoors, spend little time outdoors, use high sun protection consistently or live in regions with limited sunlight are at higher risk. Urban lifestyles, indoor jobs, air pollution may be contributory triggers but in India, deficiency is surprisingly common because of inadequate absorption (malabsorption) and impaired metabolism.
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Diagnosis is simple
The good news is that diagnosing vitamin D deficiency is straightforward. A simple blood test can measure serum vitamin D levels. In many cases, deficiency is discovered during routine health checkups, as in the patient story above. Once identified, treatment usually involves supplements and safe sun exposure, under medical guidance. Improvement in symptoms can take a few weeks to months, depending on how low the levels were. Follow the prescription as overload of vitamin D supplementation can result in toxicity.
What makes vitamin D deficiency tricky is that its symptoms overlap with stress, burnout and even mild depression. Many people try to fix the problem through lifestyle changes alone, unaware that a nutritional gap may be the real cause.
(Dr Chatterjee is senior consultant, Internal Medicine, Apollo Hospital, Delhi)
