What To Expect
The 25-hydroxy vitamin D test involves providing a blood sample. To take a blood sample, a healthcare provider will first clean the skin on the persons arm. Then they will draw blood using a needle.
When they have collected enough blood, the healthcare provider will remove the needle and apply pressure to the wound. They will then dress it with a Band-Aid or bandage.
A 25-hydroxy vitamin D test is safe and usually does not cause side effects. However, some people may feel faint or lightheaded after the test. Others may notice bruising or pain around the needle site, which may last several days.
one-quarter of adults in the U.S. were at risk of vitamin D deficiency.
Low vitamin D can cause a range of problems. In children, a vitamin D deficiency can cause rickets, which occurs when the bones become soft and bend. In adults, low vitamin D can lead to osteomalacia, which causes bone weakness and pain.
Certain groups are more at risk for vitamin D deficiency than others, so people belonging to them may wish to check their vitamin D levels with a test. These individuals include :
- older adults and people with darker skin, as their skin is less able to synthesize vitamin D from sunlight
- people with obesity, as fat cells can bind to vitamin D and prevent it from entering the bloodstream
- people with osteoporosis, celiac disease, and other conditions that interfere with vitamin D absorption
- people who have had gastric bypass surgery
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
- older adults
- 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.
How Is The 25
Your doctor will tell you not to eat anything for four to eight hours before the test.
The 25-hydroxy vitamin D test requires a common blood test. Your healthcare provider will draw blood from a vein in your arm using a needle. A quick finger prick will more than likely provide enough for a blood sample in children and infants.
Results will depend on your age, sex, and the testing methods used. Results can also slightly vary from lab to lab.
According to the , levels of vitamin D are measured by the 25-hydroxy level in nanomoles/liter or nanograms/milliliter . The results can indicate the following:
- deficiency: less than 30 nmol/L
- potential deficiency: between 30 nmol/L and 50 nmol/L
- normal levels: between 50 nmol/L and 125 nmol/L
- high levels: higher than 125 nmol/L
If your vitamin D levels are low and youre having symptoms of bone pain, a doctor may recommend a special scan to check bone density. Doctors use this painless scan to evaluate a persons bone health.
Low blood levels of 25-hydroxy vitamin D usually mean one of the following:
- you arent eating a balanced, complete diet
- your intestines arent absorbing the vitamin properly
- youre not spending enough time outside to absorb adequate vitamin D levels through sun exposure
Some evidence links vitamin D deficiency to a higher risk of certain cancers, immune diseases, and cardiovascular disease.
High levels are rarely due to consuming too much of the vitamin through foods or sun exposure.
- excessive bleeding
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What Happens During A Vitamin D Test
A vitamin D test is a blood test. During a blood test, a health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
Does The Intake Of Other Fat
It has been hypothesized that two other fat-soluble vitamins, vitamin K and vitamin A, may play important roles in vitamin D toxicity.
Vitamin K helps regulate where calcium ends up in the body, and high amounts of vitamin D may deplete the bodys stores of vitamin K (
36 ).
Keep in mind that these are just hypotheses, but it may be wise to make sure youre getting enough of these nutrients if youre going to supplement with vitamin D.
Summary
If youre supplementing with vitamin D, then it may be important to also ensure sufficient intake of vitamin A, vitamin K, and magnesium. These may reduce the risk of adverse effects from a higher vitamin D intake.
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Your Value Is Between 80
These values are only slightly above those that can be achieved naturally by exposing the skin to the sunlight. It is assumed that these values cannot be achieved without taking vitamin D in dietary supplement form. To date, no risks are known which would result from consistently high values in the range of 80-100 ng/ml.
What Abnormal Results Mean
A lower-than-normal level can be due to a vitamin D deficiency, which can result from:
- Lack of skin exposure to sunlight, darkly pigmented skin, or consistent use of high-SPF sunscreen
- Lack of enough vitamin D in the diet
- Liver and kidney diseases
- Poor food absorption
- Use of certain medicines, including phenytoin, phenobarbital, and rifampin
- Poor vitamin D absorption due to advanced age, weight-loss surgery, or conditions in which fat is not absorbed well
A low vitamin D level is more common in African American children , as well as in infants who are breastfed only.
A higher-than-normal level may be due to excess vitamin D, a condition called hypervitaminosis D. This is most commonly caused by taking too much vitamin D. It can result in too much calcium in the body . This leads to many symptoms and kidney damage.
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What Is Being Tested
Vitamin D is a family of compounds that is essential for the proper growth and formation of teeth and bones. This test measures the level of vitamin D in the blood.
Two forms of vitamin D can be measured in the blood, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D. The 25-hydroxyvitamin D is the major form found in the blood and is the relatively inactive precursor to the active hormone, 1,25-dihydroxyvitamin D. Because of its long half-life and higher concentration, 25-hydroxyvitamin D is commonly measured to assess and monitor vitamin D status in individuals.
Vitamin D comes from two sources: endogenous, which is produced in the skin on exposure to sunlight, and exogenous, which is ingested in foods and supplements. The chemical structures of the types of vitamin D are slightly different, and they are named vitamin D2 and vitamin D3 . The D2 form is found in fortified foods and in most vitamin preparations and supplements. Vitamin D3 is the form produced in the body and is also used in some supplements. Vitamin D2 and D3 are equally effective when they are converted by the liver and the kidney into the active form, 1,25-dihydroxyvitamin D.
Some tests do not distinguish D2 and D3 forms of the vitamin and report only the total result. Newer methods, however, may report levels of both D2 and D3 and then add them together for a total level.
Vitamin D Toxicity: How Does It Happen
Vitamin D toxicity implies that vitamin D levels in the body are so high that they cause harm.
Its also termed hypervitaminosis D.
Vitamin D is a fat-soluble vitamin. In contrast to water-soluble vitamins, the body has no easy way of getting rid of fat-soluble vitamins.
For this reason, excessive amounts may build up inside the body.
The exact mechanism behind vitamin D toxicity is complicated and isnt fully understood at this point.
However, we know that the active form of vitamin D functions in a similar way as a steroid hormone.
It travels inside cells, telling them to turn genes on or off.
Usually, most of the bodys vitamin D is in storage, bound to either vitamin D receptors or carrier proteins. Very little free vitamin D is available (
- Sufficient: 2030 ng/mL, or 5075 nmol/L
- Safe upper limit: 60 ng/mL, or 150 nmol/L
- Toxic: above 150 ng/mL, or 375 nmol/L
A daily vitamin D intake of 1,0004,000 IU should be enough to ensure optimal blood levels for most people.
Summary
Blood levels in the range of 2030 ng/mL are usually considered sufficient. The safe upper limit is considered to be about 60 ng/mL, but people with symptoms of toxicity usually have levels above 150 ng/mL.
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Vitamin D And 25 Vitamin D Clinical Utilities
As rightly said even though 1,25-Dihydroxy vitamin D is the most potent vitamin D metabolite, levels of the 25-OH forms of vitamin D more accurately reflect the body’s vitamin D stores. Consequently, 25HDN / 25-Hydroxyvitamin D2 and D3, in serum are the preferred initial test for assessing vitamin D status.
However being a biologically active form, 1,25 2 Vitamin D stimulates calcium absorption in the intestine and its production is tightly regulated through concentrations of serum calcium, phosphorus, and parathyroid hormone.
But in the presence of renal disease, 1,25-dihydroxy vitamin D levels may be needed to adequately assess vitamin D status. The metabolite is checked for monitoring vitamin D therapy in patients with chronic kidney disease, who may have normal 25D levels. As kidney disease progresses, the ability of the kidney to produce 1,252D decreases supplementation with vitamin D is thus no longer effective, and patients require administration of 1,252D.
Below is the list of conditions when decreased level of 1, 25 2 Vitamin D is seen:
1) CKD due to impaired production of 1 alpha hydroxylase production the test can be indicative of early kidney failure
2) Heritable disorders like D dependent rickets type by mutation in 1 alpha hydroxylase.
3) Tumor induced osteomalacia due to tumor secreted FGF23 inhibits enzyme 1 alpha hydroxylase.
4) Use of HIV protease inhibitors
Below is the list of conditions when increased level of 1, 25 2 Vitamin D is seen:
Vitamin D At First Follow
Of 1651 patients who had suboptimal serum 25D levels at baseline, 799 were available for follow up assessment providing a follow-up rate of 48.4%. Patients available for first follow-up differed from those not available with regard to several baseline characteristics such as cancer type, stage, gender and treatment history as reported in Table . The mean time duration between baseline and first follow-up assessment was 14.7 weeks . There were no episodes of intolerance to vitamin D and no toxicity was reported or observed in any patient. Of 799 patients, 441 were responders and 358 were non-responders at first follow-up. Supplementation was continued at 8000 IU/day for another 8 weeks for non-responders while responders were put on a maintenance dose of 2000 IU/day. The results for second follow-up after 8 weeks are not available yet and therefore not included in the present analysis. Table compares the mean scores of 25D at baseline and first follow-up in these 799 patients for all cancers combined as well as stratified by the top 5 cancer sites. The difference in means across the two time points was statistically significant in the total sample as well as within each stratum of cancer type. The highest improvement in mean serum levels was observed in lung cancer patients while lowest improvement was seen in colorectal cancer patients , the difference being statistically significant.
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Can You Ever Have Too Much Vitamin D
Yes. You can get too much vitamin D if you overdo the supplements. Interestingly, you cannot get too much vitamin D from the sun. Vitamin D toxicity is, thankfully, quite rare but can lead to hypercalcemia and together the symptoms can include:
- Confusion.
- Ataxia .
Do not take higher-than-recommended doses of vitamin D without first discussing it with your doctor. However, your doctor might recommend higher doses of vitamin D if he or she is checking your blood levels and adjusting your dose accordingly. Also, be cautious about getting large doses of vitamin A along with the D in some fish oils. Vitamin A can also reach toxic levels and can cause serious problems.
Vitamin D At Baseline
2198 patients were tested between January 2008 and December 2009 at MRMC. Table describes the baseline characteristics of our patient population stratified by serum 25D levels using a cut-off of 32 ng/ml. Of 2198 patients, 1651 were suboptimal in baseline serum 25D . Over 70% of both new and previously treated patients were suboptimal suggesting that the prevalence of suboptimal levels is not related to treatment history. Colorectal cancer patients had the highest prevalence of suboptimal vitamin D while breast cancer patients had the lowest . Table compares the mean values of baseline serum 25D across different types of cancers. Consistent with the results reported in Table , patients with breast cancer were found to have the highest average 25D levels of 27.9 ng/ml whereas those with colorectal cancer were found to have the lowest average of 21.6 ng/ml. When comparing the mean values of baseline serum 25D across gender, prior treatment history and stage at diagnosis, we found no statistically significant relationship between any of these covariates and serum 25D levels. Finally, there was no correlation between age at presentation and baseline 25D levels .
Table 1 Baseline patient characteristics
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What Other Factors Can Lead To Vitamin D Deficiency
- Age: The skin’s ability to make vitamin D lessens with age.
- Mobility: People who are homebound or are rarely outside are not able to use sun exposure as a source of vitamin D.
- Skin color: Dark-colored skin is less able to make vitamin D than fair-colored skin.
- Human breast milk: A woman’s breast milk only contains a small amount of vitamin D. Often infant formulas also only include a small amount of D also. Therefore infants are at risk of not receiving enough vitamin D. This is especially true for infants who are only fed breast milk.
Your Value Is Between 10
Vitamin D deficiency is still present, along with increased risk of developing osteoporosis. Parathyroid hormone levels are likely to be elevated. This hormone regulates calcium and phosphorus levels in the body.
If your vitamin D blood level is e.g. 25 ng/ml or higher and you want to increase them, you can take the following amount of vitamin D :
To reach the mentioned value.. take this vitamin D Dose per day:
20 ng/ml ..500 IU 30 ng/ml ..1700 IU 40 ng/ml ..3200 IU 50 ng/ml ..4900 IU 60 ng/ml ..7000 IU 70 ng/ml ..9700 IU
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Causes Of Vitamin D Deficiency
Vitamin D deficiency can occur for a number of reasons:
You don’t consume the recommended levels of the vitamin over time. This is likely if you follow a strict vegan diet, because most of the natural sources are animal-based, including fish and fish oils, egg yolks, fortified milk, and beef liver. Here are the best vitamin d foods for vegetarians.
Your exposure to sunlight is limited. Because the body makes vitamin D when your skin is exposed to sunlight, you may be at risk of deficiency if you are homebound, live in northern latitudes, wear long robes or head coverings for religious reasons, or have an occupation that prevents sun exposure. Duirng the winter, vitamin D deficiency can be more prevalent because there is less sunlight available.
Continued
You have dark skin. The pigment melanin reduces the skin’s ability to make vitamin D in response to sunlight exposure. Some studies show that older adults with darker skin are at high risk of vitamin D deficiency.
Your kidneys cannot convert vitamin D to its active form. As people age, their kidneys are less able to convert vitamin D to its active form, thus increasing their risk of vitamin D deficiency.
Your digestive tract cannot adequately absorb vitamin D. Certain medical problems, including Crohn’s disease, cystic fibrosis, and celiac disease, can affect your intestine’s ability to absorb vitamin D from the food you eat.
Definition Of Vitamin D Insufficiency And Deficiency
There is no absolute consensus as to what a normal range for 25D should be. Part of the difficulty is how a normal range is determined, i.e., typically it is done by obtaining blood from several hundred volunteers and deeming them to be normal and to perform the measurement of the analyte and do a distribution with a mean ± 2SD as the normal range. However, since it is now recognized that 30-50% of both the European and US population are vitamin D insufficient or deficient, the previously reported normal ranges of 10-55 ng/ml are totally inadequate.1, 4, 16, 20–23 Chapuy et al24 reported that a dot plot of serum 25D levels as a function of PTH levels provided an insight as to what the serum 25D levels should be to be considered sufficient. They observed that the PTH levels began to plateau at their nadir when 25D levels were between 30-40 ng/ml. A similar observation was made by Thomas et al and Holick et al.14
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