Here are the 10 signs to know:

1) You're often sick. There is a link between Vitamin D deficiency and an increased risk of both upper and lower respiratory tract infections such as pneumonia, as well as an increase in the common cold and flu.

2) You're fatigued. Although there are many reasons for feeling tired, a lack of Vitamin D can be one of them. Try taking a Vitamin D supplement to see if your energy levels increase.

3) Your bones ache. This complaint is a classic symptom of Vitamin D deficiency, especially when paired with fatigue. Vitamin D is needed for calcium absorption into the collagen matrix of your skeleton.

4) Your bones break often. Vitamin D is proven to promote bone growth, and a deficiency in the vitamin can result in weaker bones and an increased risk of fractures. Some studies have shown that in the case of extremely low Vitamin D, fractures were twice as likely to occur.

5) You feel depressed. Humans have long known about the link between sunlight and depression. Vitamin D plays a role in regulating adrenaline, noradrenaline, and dopamine production in the brain, and it protects against the depletion of serotonin. Although the scientific studies are in the early stages, Vitamin D deficiencies have so far been associated with an 8–14% increase in depression.

6) You're gaining weight. If it's not related to your diet or another health issue, weight gain could be related to a lack of Vitamin D. Although not clearly understood yet, there is a proven link between Vitamin D deficiencies and weight gain. Conversely, studies have shown that Vitamin D supplements assist with weight loss when combined with a diet and exercise program.

7) Your wounds are slow to heal. Vitamin D is essential for the forming of new skin during the wound-healing process. It also has a role to play in fighting infection and controlling inflammation, both of which can jeopardize the healing of wounds.

8) Excessive sweating. Although this sounds unusual, "head sweating" is one of the most common symptoms of early Vitamin D deficiencies, especially among infants. A sweaty forehead and an inability to regulate temperature are common among adults with a Vitamin D deficiency, too.

9) Your muscles are unexpectedly weak... This is especially important in older people. A Harvard study found adults treated with Vitamin D had greater muscle control and 20% fewer falls.

10) ...and your muscles hurt. There is some evidence to say that low Vitamin D levels are linked to muscle pain. A study in which 71% of people with chronic muscle pain were found to be deficient in Vitamin D. Another study found that children reported their growing pains to be reduced by 57%, on average, after being treated with Vitamin D supplements.

If identified early and treated quickly, a Vitamin D deficiency isn't a serious matter. It's as simple as getting a little more sunlight on your unprotected skin, eating a diet rich in Vitamin D (such as fatty fish, cheese, and eggs), or taking common supplements available from the pharmacy. However, because the symptoms are often so subtle and easily mistaken for other issues, Vitamin D deficiencies regularly go undiagnosed and the long term risks are significant. If you're experiencing the above signs of a deficiency, or if you'd like to try a Vitamin D supplement, consult your doctor first.

RESOURCES WEBMD, MERCOLA, MEDICINE NET, AUTHORITY NUTRITION, PREVENTION, WOMENS HEALTH MAG, AND NATURAL NEWS

Featured image source: Pixabay