Most people with low vitamin D feel nothing unusual at all — that's part of what makes it easy to miss. When symptoms do show up, they tend to be quiet and easy to blame on something else.
None of the points below are a checklist to self-diagnose against. Fatigue, aches and low mood all have plenty of causes that have nothing to do with vitamin D. The only way to know what's actually going on with your levels is a blood test with your doctor — please don't use this page to draw conclusions about your own health.
Tiredness that doesn't track with how much you slept.
A dull, ongoing ache rather than an injury.
Aching or weak muscles, sometimes cramping.
Catching colds or infections more than usual.
Especially during long stretches of indoor, low-light days.