Like other steroid hormones, DHVD binds to a nuclear receptor, influencing gene transcription patterns in target organs. Based on these considerations circulating 25HDN is the best indicator of optimal vitamin D body stores.
The exact levels of optimal circulating 25HDN concentrations remain a matter of debate. Mild-to-modest deficiency can be associated with osteoporosis or secondary hyperparathyroidism. Severe deficiency may lead to failure to mineralize newly formed osteoid in bone, resulting in rickets in children and osteomalacia in adults.
The consequences of vitamin D deficiency on organs other than bone are not fully known, but might include increased susceptibility to infections, muscular discomfort, and an increased risk of colon, breast, and prostate cancer. Although much less common, severe deficiency is not rare either. Reasons for suboptimal 25HDN levels include lack of sunshine exposure, a particular problem in Northern latitudes during winter; inadequate intake; malabsorption eg, due to celiac disease ; depressed hepatic vitamin D hydroxylase activity, secondary to advanced liver disease; and enzyme-inducing drugs, in particular many antiepileptic drugs, including phenytoin, phenobarbital, and carbamazepine, which increase 25HDN metabolism.
Patients with renal failure can have very high OH-VitD levels without any signs of toxicity, as renal conversion to the active hormone 1,OH-VitD is impaired or absent. These reference ranges represent clinical decision values, based on the Institute of Medicine report, that apply to males and females of all ages, rather than population-based reference values. Population reference ranges for OH-VitD vary widely depending on ethnic background, age, geographic location of the studied populations, and the sampling season.
Population-based ranges correlate poorly with serum OH-VitD concentrations that are associated with biologically and clinically relevant vitamin D effects and are therefore of limited clinical value. A study on Australian office workers found that applying sunscreen meant people could spend more time outdoors, leading to higher vitamin D levels overall. People can also get some of their vitamin D from food. According to the Office of Dietary Supplements , food sources of vitamin D include:.
The study on Australian office workers found that fish consumption, in particular, had a positive effect on vitamin D levels during winter. A person can take too much vitamin D. Since vitamin D occurs naturally in only a few food sources, the most likely way a person can get too much vitamin D is through taking a high strength supplement. According to one study , vitamin D toxicity can produce symptoms that include:. The upper limits for how much vitamin D a person should take per day by age, are as follows:.
A person should see a doctor if they notice the symptoms of vitamin D toxicity. A person should also see their doctor if they notice symptoms of a lack of vitamin D. A doctor may do a physical examination, ask questions, or perform a blood test to see if the person has a deficiency.
People aged 1—70 years should aim to get at least 15 mcg or IU of vitamin D per day. Those who are older or at risk for a deficiency may require more.
Vitamin D is an essential nutrient for a variety of reasons, particularly for bone health. A person will often get enough vitamin D from sunlight, but if they are at risk for a deficiency, they may benefit from taking a supplement. The body produces vitamin D in response to sun exposure. Vitamin D has a range of benefits. Why do I need a vitamin D test? These symptoms include: Bone weakness Bone softness Bone malformation in children Fractures The test may be ordered if you are at a higher risk for a vitamin D deficiency.
Risk factors include: Osteoporosis or other bone disorder Previous gastric bypass surgery Age; vitamin D deficiency is more common in older adults. Obesity Lack of exposure to sunlight Having a darker complexion Difficulty absorbing fat in your diet In addition, breastfed babies may be at a higher risk if they aren't taking vitamin D supplements. What happens during a vitamin D test? Will I need to do anything to prepare for the test?
You don't need any special preparations for a vitamin D test. Are there any risks to the test? What do the results mean? If your results show a deficiency in vitamin D, it may mean you are: Not getting enough exposure to sunlight Not getting enough vitamin D in your diet Having trouble absorbing vitamin D in your food A low result may also mean your body is having trouble using the vitamin as it should, and may indicate kidney or liver disease.
To learn what your results mean, talk to your health care provider. Is there anything else I need to know about a vitamin D test? Sunlight exposure and supplements are two other main sources of vitamin D that will contribute to reaching an optimal vitamin D status for health.
Those of you who are not living in a sunny climate year-round will be hard-pressed to maintain a healthy level of vitamin D by relying on sunlight alone. Reference Range. The reference range, a term often used in conjunction with laboratory testing, is a set of values that include the upper and lower limits of a lab test based on a group of otherwise healthy individuals.
For a laboratory to determine the appropriate reference range for their testing population, often hundreds to thousands of normal, healthy patients are tested. To date, ZRT has tested over 60, patients to assess their vitamin D levels. This raises the issue: is normal the same thing as optimal? Not necessarily. The Endocrine Society has a Clinical Practice Guideline on the evaluation, treatment, and prevention of vitamin D deficiency.
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