Vitamin D deficiency rarely announces itself with drama. It builds slowly, almost quietly, until small changes begin to feel like a pattern. A lingering tiredness. A low mood that does not quite lift. A body that feels heavier than usual. These are easy to dismiss as stress or routine fatigue. But sometimes, the body is signalling something deeper.Functional Nutritionist Mugdha Pradhan, CEO & Founder of iThrive, puts it simply: “Vitamin D isn’t just a vitamin, rather it behaves more like a hormone. And when it’s low, the body feels it quietly before it feels it loudly.”