Calcium is short in a surprising number of diets. Global estimates suggest around 43% of people don't get enough, high for a mineral most people assume they're covered on.
Its job is structural: calcium keeps your bones and teeth strong, and it helps your muscles and nerves function. The catch is that when your intake falls short, your body pulls what it needs from your bones to keep everything else running, so there's often no signal in the moment. Over the long term, low intake is associated with weaker bones, but you won't feel it happening, which is exactly why it's worth tracking rather than assuming.
Most adults need around 1,000 mg a day, and it's best not to exceed 2,500 mg. Dairy is the classic source, with milk, yoghurt, and cheese all strong, alongside sardines, leafy greens, and fortified foods.
A note on age: women over 50 need more, around 1,200 mg daily, and for anyone 51 and older the upper limit steps down to 2,000 mg.