I will second that vitamin D is the one big exception, both because deficiency is so common and the symptoms are so easy to miss.
Granted it’s still good to get checked and have your doctor tell you your dose, I’ve had a partner and a friend who both needed particularly high doses. But my partner would not even have thought to ask if not for that friend, even though the deficiency was serious.
He was already getting treated for depression but no one thought to make sure his vitamin D wasn’t also super low, which it was.
