When Should I Get A Vitamin D Test
Vitamin D testing is ordered to determine if a deficiency, insufficiency, or toxic level of vitamin D is present or to monitor treatment for a previously diagnosed deficiency.
Your health care provider may order a vitamin D blood test for you if you are experiencing symptoms of a vitamin D deficiency, such as:
- Weakening of the bones
- History of weight loss surgery
- Reduced ability to make vitamin D in the skin due to limited sun exposure, sunscreen use, or dark skin pigmentation
- Digestive diseases that make it difficult to absorb nutrients from food, including celiac disease and Crohnâs disease
- Kidney and liver disease
- Use of certain medications
Vitamin D tests may also be ordered if your health care provider suspects that you may have abnormally high vitamin D levels, known as vitamin D toxicity. This occurs as a result of taking too much vitamin D in supplements rather than from too much sun exposure or dietary intake.
Excess vitamin D in supplement form may cause your body to absorb more calcium from food and to reabsorb calcium from the bones into the blood. This results in excess calcium in the blood, also known as hypercalcemia, which can lead to symptoms like fatigue, confusion, bone pain, nausea and vomiting, frequent urination, and kidney problems.
A health care provider who is familiar with your medical history is in the best position to determine whether you might benefit from vitamin D testing.
Linus Pauling Institute Recommendation
The Linus Pauling Institute recommends that generally healthy adults take 2,000 IU of supplemental vitamin D daily. Most multivitamins contain 400 IU of vitamin D, and single-ingredient vitamin D supplements are available for additional supplementation. Sun exposure, diet, skin color, and body mass index have variable, substantial impact on body vitamin D levels. To adjust for individual differences and ensure adequate body vitamin D status, the Linus Pauling Institute recommends aiming for a serum 25-hydroxyvitamin D concentration of at least 30 ng/mL . Observational studies suggest that serum 25-hydroxyvitamin D concentrations between 30 ng/mL and 60 ng/mL are associated with lower risks of adverse health outcomes, including cancers and autoimmune diseases.
The American Academy of Pediatrics currently suggests that all infants, children, and adolescents receive 400 IU of supplemental vitamin D daily . Consistent with the recommendations of the Endocrine Society , the Linus Pauling Institute recommends daily intakes of 400 to 1,000 IU of vitamin D in infants and 600 to 1,000 IU of vitamin D in children and adolescents. Given the average vitamin D content of breast milk, infant formula, and the diets of children and adolescents, supplementation may be necessary to meet these recommendations.
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However, all these foods in addition contain the metabolite 25-hydroxyvitamin D . Contents are typically very low in milk and fish , somewhat higher in meat and offal and up to 1 microg/100 g in egg yolk. Thus, the biological activity of 25OHD is greater than that of native vitamin D. However, there is as yet no consensus on the conversion factor that should be used for 25OHD to calculate vitamin D activity.If food contents and the higher potency of 25OHD are not included in dietary intake surveys, true vitamin D intake will be underestimate.
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How Is Vitamin D Deficiency Diagnosed
Healthcare providers dont usually order routine checks of vitamin D levels, but they might need to check your levels if you have certain medical conditions or risk factors for vitamin D deficiency and/or have symptoms of it.
Your provider can order a blood test to measure your levels of vitamin D. There are two types of tests that they might order, but the most common is the 25-hydroxyvitamin D, known as 25D for short.
Prevalence Of Vitamin D Deficiency And Vitamin D Insufficiency By Season
The mean levels of serum 25D changed according to season. The levels of 25D gradually increased in the order of winter, spring, autumn and summer . The mean level of serum 25D in spring was similar to that of autumn . There were no significant differences between the mean serum 25D levels in the two groups above. The prevalence of vitamin D sufficiency during the four seasons was 28.3, 41.5, 25.1 and 21.0% .
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What Do My Test Results Mean
High test results in the Vitamin D 25-hydroxy blood test are extremely rare and toxicity levels are even more rare. High results are typically because of supplements being taken. Because of this, most results are reported as either ânormalâ or âdeficient.â An individual can be deficient in one or in both vitamins. Normal results for Vitamin D are anything above 30 ng/mL, while normal results for the 25-hydroxyvitamin are anything above 20 ng/mL.
Normal results typically mean no further testing is necessary. If there are physical symptoms being investigated, a normal result excludes these two vitamins from the cause.
If there is a deficiency present, then the most common reasons are because of a dietary issue or that someone isnt getting enough sunlight exposure during the day. Certain drugs, such as Dilantin, have also been known to interfere with 25-hydroxy production. It can also be an indication that kidney disease has developed. Low levels of 25-hydroxy are one of the earliest changes associated with early kidney failure.
Although high Vitamin D levels can lead to calcification, the danger is that magnesium levels are too low. This creates a calcium that is resistant to the vitamin and can create calcification even though the blood test results came back as normal.
How Much Does The Test Cost
The cost of vitamin D blood testing depends on where you have the test taken, whether other tests are performed at the same time, and whether you have health care coverage.
The costs of testing may include an office visit, a blood draw fee, and charges from the laboratory analyzing your blood sample. These costs are usually covered by insurance when the test is ordered by your health care provider. However, you may wish to check with your health insurance company to learn whether you are responsible for a deductible or copay.
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Similarities Between Vitamin D And D3
Vitamin D and D3 are both ultimately metabolized to the active metabolite form, calcitriol. From calcitriol come the important end results of a healthy level of vitamin D in your body. Calcitriol promotes renal absorption of calcium, increases intestinal absorption of both calcium and phosphorus, and increased mobilization of calcium from bone to plasma. Calcitriol has even been shown to inhibit cancer cell growth. Ultimately both vitamin D and D3 provide your body with the critical metabolite, calcitriol.
Are Vitamin D Or D3 The Same
When we refer to vitamin D, we are talking about Vitamin D2. Vitamin D2 and D3 are both widely used vitamin D supplements but are not the same. Vitamin D2 is ergocalciferol and comes from plant-based sources. Vitamin D3 is cholecalciferol and comes from animal-based sources. Both supplements are processed in the body by the liver to 25-hydroxyvitamin D, though vitamin D3 is thought to provide higher levels of 25D. Some formulations of vitamin D2 are prescription only, while all formulations of vitamin D3 are over-the-counter.
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Why Normal Levels Can Differ Across Different Labs
Each laboratory must establish its own normal ranges for vitamin D in the blood. These ranges depend on the makeup of the local population, the technologies used and the accuracy of the measurement. There may be also slight differences in the normal levels, according to age, gender, race or ethnic origin, geographic region, diet, type of sample and other relevant status.
Your doctor will study the results along with your medical record, screenings, physical condition, symptoms and any other relevant information about your situation.
Vitamin D levels depend on the exposure to the sunlight. They show seasonal variation with the highest concentrations in summer or fall and the lowest concentrations in winter or spring. In addition, the production of vitamin D has been reported to decrease with age.
The values shown above refer to the 25-hydroxy vitamin D test which is the main circulating form of vitamin D in the blood. However, there is also a test to measure the 1,25-dihydroxyvitamin D in the blood and the normal ranges for it are 15 to 60 pg/mL .
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Why Is A 25
Your doctor may request a 25-hydroxy vitamin D test for several different reasons. It can help them figure out whether too much or too little vitamin D is causing bone weakness or other abnormalities. It can also monitor people who are at risk for having a vitamin D deficiency.
Those who are at high risk of having low levels of vitamin D include:
- people who dont get much exposure to the sun
- babies who are breastfed only
- people who have had gastric bypass surgery
- people who have a disease that affects the intestines and makes it difficult for the body to absorb nutrients, such as Crohns disease
Your doctor may also want you to do a 25-hydroxy vitamin D test if theyve already diagnosed you with a vitamin D deficiency and want to see if treatment is working.
Symptoms And Health Risks Of Vitamin D Deficiency
Symptoms of bone pain and muscle weakness can mean you have a vitamin D deficiency. Low blood levels of the vitamin have been associated with the following: Increased risk of death from cardiovascular disease
Cognitive impairment in older adults
Severe asthma in children
Cancer Research suggests that vitamin D could play a role in the prevention and treatment of a number of different conditions, including type1 and type 2 diabetes, hypertension, glucose intolerance, and multiple sclerosi.
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Is Vitamin D Or D3 More Effective
Vitamin D2 and D3 are absorbed into the bloodstream where they are metabolized by the liver into 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3, otherwise collectively known as 25D or calcifediol. Calcifediol is the vitamin D complex circulating in your blood, and its levels directly reflect your bodys stores of vitamin D. Calcifediol is commonly referred to as the active form of vitamin D. When your doctor orders lab tests to check your vitamin D levels, they are measuring your calcifediol levels. Calcifediol is the precursor to calcitriol, the ultimate active metabolite of vitamins D and D3.
There have been several studies comparing whether supplementation with vitamin D2 or D3 produces a higher blood level of calcifediol. A study published by the National Institutes of Health was conducted in elderly, post-menopausal women who had been identified as vitamin D deficient. It compared the effects of receiving a single high dose of vitamin D2 or vitamin D3 on calcifediol levels. The study concluded that vitamin D3 produced about twice the amount of circulating calcifediol in this patient population versus that of vitamin D2.
In a separate clinical trial comparing a 10-week regimen of twice weekly 50,000 IU dosing of both vitamin D2 and vitamin D3 in demographically matched groups, vitamin D3 was also found to be superior in producing higher levels of 25D, or calcifediol.
How Can I Prevent Vitamin D Deficiency
The best way to prevent vitamin D deficiency is to ensure youre getting enough vitamin D in your diet and/or through sun exposure. But be careful about being in the sun for too long without sunscreen. Excessive sun exposure puts you at an increased risk for skin cancer.
The amount of vitamin D you need each day depends on your age. The average daily recommended amounts are listed below in micrograms and International Units .
|Age / Life Stage|
You can also get vitamin D from fortified foods. Be sure to check the nutrition labels to find out if a food has vitamin D. Foods that often have added vitamin D include:
- Cows milk and soy, almond and oat milk.
- Breakfast cereals.
- Other dairy products, such as yogurt.
Vitamin D is in many multivitamins. There are also vitamin D supplements.
Talk to your healthcare provider if youre concerned about getting enough vitamin D.
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Measurement Of The Vitamin D Content Of Meat
The vitamin D3, 25D3, vitamin D2, and 25D2 contents of the meat samples were analyzed using a modification of a sensitive LC-tandem MS method, as described in detail elsewhere . The extraction procedure for the analysis was a modification from a previously published method , which included an overnight saponification and solid phase extraction followed by 4-phenyl-1,2,4-triazoline-3.5-dione derivatization. The methodâs limit of detection for vitamin D3, vitamin D2, 25D3, and 25D2 was 0.007, 0.009, 0.003, and 0.007 g/100 g, respectively. The National Institute of Standards and Technology standard reference material no. 1546a: Meat Homogenate was analyzed for the 4 vitamin D compounds so that a comparison could be made with its reference vitamin D3 and certified 25D3 values.
The total vitamin D activity of meat was defined as . The conversion factor of 5 is applied to the 25D3 content on the basis of efficacy data from a randomized controlled trial with oral vitamin D3 and 25D3 in healthy adults , and is a factor commonly used in a number of food composition tables . It should be noted, however, that equivalent data do not exist for vitamin D2 and 25D2, so we assumed a conversion factor of 5 in our calculation of the total vitamin D activity of meat .
Who Is Most At Risk For Vitamin D Deficiency
Aside from medical conditions that can lead to vitamin D deficiency, biological and environmental factors that put someone at an increased risk of vitamin D deficiency include:
- Age: Your skin’s ability to make vitamin D decreases with age, so people over the age of 65 years are especially at risk for vitamin D deficiency. Infants are also at risk of not receiving enough vitamin D. This is especially true for infants who are only fed breast milk, as it contains only a small amount of vitamin D.
- Skin color: Its more difficult for dark-colored skin to make vitamin D from sunlight than light-colored skin, so people with darker skin are at a higher risk for vitamin D deficiency.
- Mobility: People who are homebound or rarely go outside arent able to use sun exposure as a source of vitamin D. Thus, theyre at a higher risk for vitamin D deficiency.
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The Zrt Laboratory Blog
If you have ever had your level of Vitamin D tested, depending on which lab you used, your report showing whether your level is low, normal, or high might have left you scratching your head. In fact, there are multiple agencies all with slightly different opinions on what levels are deficient, insufficient, sufficient, high, or toxic.
When testing with ZRT, you will receive a result that is reflective of your total 25-Hydroxy Vitamin D status in blood. This is the storage form of vitamin D, which is converted by the kidneys to the biologically active form, 1,25-dihydroxycholecalciferol.
Vitamin D3 is involved in numerous biological processes such as immune system modulation, insulin sensitivity, hormone and neurotransmitter homeostasis, and is essential for ensuring calcium absorption in the bones. Dietary sources of vitamin D include foods such as cows milk, fish, egg yolk, and pork. 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.
Based On Years Of Patient Testing And Data Analysis We Have Updated Our Laboratory Report Reference Range To Reflect That Values Between 20
This raises the issue: is normal the same thing as optimal? Not necessarily. The Vitamin D Council places the ideal level between 40 and 80 ng/mL with levels below 20 ng/mL as deficient. The Endocrine Society has a Clinical Practice Guideline on the evaluation, treatment, and prevention of vitamin D deficiency. This guideline recommends a minimum vitamin D level of 20 ng/mL, but to guarantee sufficiency they recommend between 30 and 50 ng/mL for both children and adults. In contrast, the Vitamin D Council states that even levels between 30 and 40 ng/mL are still not quite sufficient. On the other end of the spectrum, results that fall between 80 and 100 ng/mL are not achievable naturally that is, they are only reached with some form of vitamin D supplementation. So, while they are not harmful levels, they are instead reflective of supplementation and therefore not what would be detected in a normal patient population.
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