Vitamin D deficiencies have become common among the general population.Why?Well, long story short: Our modern lifestyle does not allow for enough time in the sunshine.What’s more, only a small number of foods contain vitamin D, meaning our ability to get vitamin D nutritionally is a tough gig. Like most vitamins or nutrients, when you’re unable to get a healthy level from your diet, that’s where supplements come in!We tend to feel these deficiency effects more harshly due to the significant role vitamin D plays in the body - considering it affects almost every cell.This is because vitamin D regulates gene expression and can modulate hundreds if not thousands of our genes, influencing every organ in the body. This is why vitamin D has such a wide range of health benefits and can manifest in a wide range of symptoms if you become deficient.This brings us to the golden question: are you vitamin D deficient? Here are the common signs you may be at risk.4 Symptoms of Vitamin D Deficiency1. You're Constantly TiredFollowing a study published in the Journal of Clinical Sleep Medicine (2012), it's been suggested that lower vitamin D levels are linked to daytime sleepiness.Sleep disorders, general lethargy, or a lack of energy may all be due to a vitamin D deficiency.2. You're Suffering from Symptoms of DepressionDid it ever occur to you the feeling of happiness after a day at the beach might have less to do with your newly acquired tan and more to do with the chemical sorcery happening in your own body?Vitamin D regulates adrenaline, noradrenaline, and dopamine production in the brain. It also protects against the depletion of serotonin and dopamine. Given that we have vitamin D receptors in our brains, it'll come as no surprise that vitamin D can also affect mood, and a deficiency has been associated with depression and other mental illnesses.3. You Suffer from Muscle Pain and Bone AchesA vitamin D deficiency can lead to a loss of bone density, broken or fractured bones, and osteoporosis (a bone-thinning disease).This, of course, makes sense when we consider that vitamin D helps the body absorb calcium which is vital for strong and healthy bones. Vitamin D also develops and preserves muscle strength.In fact, elderly people are more inclined to be deficient, in part, because the skin gradually loses its ability to synthesize vitamin D as the body ages.4. You Have High Blood PressureIn a study published in The Lancet: Diabetes and Endocrinology, researchers pooled 35 studies of nearly 100,000 people with a European background to test vitamin D levels and their association with blood pressure. In conclusion, they found a possible association between increased vitamin D levels and reduced blood pressure and risk of hypertension.Some research even suggests that taking vitamin D3 supplementation can help reduce blood pressure.If you can relate to any of the above signs, and think you may suffer from vitamin D deficiency, or if you're simply curious, it's advisable to arrange for a vitamin D test with your GP.How Do I Test My Vitamin D Levels?A simple blood test is all you need to work out whether you are getting sufficient amounts of vitamin D.The most common vitamin D blood analysis will test how much 25-hydroxyvitamin D is present in your system.But what on earth is 25-hydroxyvitamin D?Also known as calcidiol. When the body receives vitamin D (from the sun, food, or supplementation), the liver converts vitamin D into a storage form called 25-hydroxyvitamin D. (#science)A low level of 25- hydroxyvitamin D indicates you are not getting enough vitamin D from sun exposure or diet.It may also indicate a lack of vitamin D absorption via the intestines, or that your liver is not producing enough vitamin D. A high level of 25-hydroxyvitamin D usually reflects excess supplementation.Your doctor may also test for 1,25-dihydroxyvitamin D.A low level of 1,25-dihydroxyvitamin D can indicate kidney diseaseA high level of 1,25-dihydroxyvitamin D may occur when there is excess parathyroid hormone or when there are diseases, such as sarcoidosis or some lymphomas, that can make 1,25-dihydroxyvitamin D outside of the kidneysHow Much Vitamin D Do I Need?Different organizations worldwide recommend different "optimum" daily levels of vitamin D. This is because the amount of vitamin D required for each person depends on a number of variables such as age, weight, skin tone, ethnicity, climate, the time of year (sun exposure), and diet.The Institute of Medicine (IOM) considers blood levels of 20 nanograms per milliliter (or 50 nanomoles per liter) to be sufficient. They recommend 600 to 800 IU’s (international units) of vitamin D per day for those with little or no sun exposure.The IOM set the upper intake level at 4,000 IUs daily for adults. In light of more recent research, however, the IOM’s recommendations are considered outdated.2,000 IUs of vitamin D a day would shift the average blood levels in the mid-50s to about 110 nanomoles per liter, which some researchers estimate could add years to our life expectancy.Data derived from randomized clinical trials have convinced some influential experts, such as Harvard’s Chair of Nutrition, that we should aim for vitamin D levels within this range. This may necessitate taking between 1,800 and 4,000 IUs a day for some people. Some even suggest taking 5000 IU per day!The Institute of Medicine sets the safe upper limit at 4000 IU but several studies have shown that people need 5000 IU per day and can tolerate up to 10,000 IU without any adverse effects.Learn more on how much vitamin D to take here. How to Increase Your Vitamin D Levels Vitamin D can be absorbed by the body in the supplement form of vitamin D2 and D3. However, vitamin D3 is far superior in absorbability and efficacy, so much so that it's twice as effective at raising vitamin D levels in the body than vitamin D2.Therefore, we recommend taking a vitamin D3 (not D2) with at least 2000 IUs per serving. It's also important to decide whether you're okay with taking a conventional vitamin D3 (made from lanolin) or if you'd prefer a plant-based option made from lichen. Wondering what your current sunshine vitamin exposure looks like? Check out this chart by GrassRoots Health!