Vitamin D deficiency symptoms may not be obvious. If you notice any of these signs, consider seeing a doctor for a vitamin D blood test.

A quick vitamin D primer

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You walk in the sunshine every day (wearing your SPF, of course). You eat right. You get enough sleep. But you still may be missing something even if you’re doing all the right things—vitamin D. Though rare, severely low levels of vitamin D can cause rickets in children and osteomalacia (softening of the bones) in adults. Left untreated, these conditions can lead to bone pain, soft and brittle bones, and muscle pain and weakness, according to the Cleveland Clinic. But recent research has suggested a connection between even moderately low levels of vitamin D and a number of surprising health conditions, including diabetes, osteoarthritis, and cancer. Here are a few sneaky vitamin D deficiency symptoms. If you feel that you’re suffering from any of these symptoms, talk with your healthcare provider, who will likely recommend a blood test. This is really the only way to accurately determine your vitamin D level. Then you can discuss ways to boost your levels, typically by taking an over-the-counter supplement.

You’re tired all the time

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If you aren’t getting enough vitamin D, you may feel completely exhausted, even if you get plenty of sleep. “There is mounting evidence that vitamin D deficiencies are associated with fatigue and sleep disorders,” says Catherine G. R. Jackson, PhD, a professor of kinesiology and exercise science at California State University in Fresno. A study in the North American Journal of Medical Sciences found that low vitamin D levels were prevalent in people who are fatigued. Taking more vitamin D helped improve their symptoms. Here are other sneaky reasons you may be tired all the time.

You’re depressed

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Having the blues may be linked to an insufficient amount of vitamin D. According to the Vitamin D Council, vitamin D receptors have been found in many parts of the brain, including in areas linked to depression. Research from the Endocrine Society showed that women with moderate to severe depression saw improvement of depression symptoms when they were treated for vitamin D deficiency symptoms—so there is a link between low levels of vitamin D in the blood and depression symptoms. But it’s still unclear exactly what that link is, whether low vitamin D levels develop because someone is depressed or whether low vitamin D levels may actually cause depression.