What does low vitamin D do to you?

Vitamin D is the bone-and-muscle vitamin with a wider résumé, and running low is common - northern latitudes, indoor lives, darker skin, older age, and covering up all cut production. NIH's Office of Dietary Supplements documents what deficiency does: the bone effects are the best proven - poor calcium absorption leading to soft, painful bones in adults and rickets in children, plus accelerated bone thinning and fracture risk. The muscle effects are next: weakness and aching that people often write off as aging. The felt cluster: fatigue, low mood, and getting sick more often - associations the evidence supports reasonably, with supplementation trials strongest in people who start out truly deficient. Testing: a simple blood test - 25-hydroxyvitamin D - settles it, worth asking about with the fatigue-and-aching cluster, a fracture from a minor fall, or heavy risk factors. The fix: supplements work reliably - typical repletion runs 1000 to 2000 IU daily, more under guidance for true deficiency; oily fish, fortified milk, and modest sunlight help; and D with a meal containing fat absorbs better. More is not better: high doses over months can push calcium too high, so megadosing without testing is a bad plan. Recheck after two to three months of repletion to confirm the level moved. Pymander is a free AI doctor, 24/7 by text. Describe your symptoms and risk factors, and it can help you decide on the test.