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Blood and urine test for vitamin D level: norm, why take it
Medical expert of the article
Last reviewed: 04.07.2025
Vitamin D is a vitamin that belongs to a group of biologically active substances, the synthesis of which occurs in the skin under the influence of ultraviolet rays. This is the main way of vitamin D penetration into the body, its intake into the body with food and vitamin complexes is considered as an auxiliary one. Sometimes the amount of vitamin can be much higher or lower than normal, which entails a number of diseases and negative consequences. The level of vitamin D in the body can be controlled. First, you need to know its exact amount in the body. For this, a vitamin D test is intended. It is recommended only as prescribed by a doctor, if necessary.
Indications for the procedure for vitamin D testing
The analysis is carried out for both children and adults. First of all, it is carried out if there is a suspicion of a deficiency of this vitamin in the body. Usually, hypovitaminosis D is accompanied by a decrease in appetite, irritability and a tearful state. Insomnia, intermittent, restless sleep may be observed. Performance is sharply reduced and fatigue increases.
Hypervitamin D levels can also have a negative effect, causing polyuria, diarrhea, and nausea. Later, muscle tissue weakens, migraines and dizziness develop, indicating intoxication of the body.
It is prescribed if a person has dystrophy, anorexia, or a sharp weight loss that cannot be controlled. The analysis is carried out in case of pancreatitis, radiation enteritis, Crohn's disease, Whipple's disease, and various types of gastritis. It is also carried out in case of various types of metabolic disorders, including gluten enteropathy, hypophosphatemia, hypocalcemia, vitamin deficiency, hypovitaminosis and hypervitaminosis D, and calcium metabolism disorders. If a person uses corticosteroids, constant monitoring of vitamin D levels is necessary. Osteoporosis, various types of skeletal disorders, and lupus erythematosus are direct grounds for the analysis.
Often the analysis is prescribed to ensure regular monitoring during treatment with vitamins and mineral complexes, which makes it possible to monitor changes in dynamics and adjust the dosage.
If the clinical picture of any disease shows signs indicating a vitamin D deficiency, it is necessary to conduct a study immediately. Rickets in children and low bone mineralization often indicate this. The analysis can be informative in dentistry: it is prescribed for caries, periodontal disease, tooth deformations, and bleeding gums. A deficiency can be indicated by postural deformation, weakness, tremor, stoop, convulsive and spasmodic conditions.
Why do you need a vitamin D test?
First of all, for timely detection of pathology, take the necessary measures. Sometimes it is useful for preventing deficiency or excess of vitamin D. The metabolism of vitamin D and calcium are closely interrelated, so it allows you to timely detect calcium metabolism disorders. In some cases, vitamin D indicators need to be monitored dynamically, for example, when treating with corticosteroids, vitamins, when treating rickets, and other diseases. It is also important for timely prevention of hypovitaminosis, since otherwise, osteoporosis may develop, the risk of fractures increases.
Where can I get tested for vitamin D?
It can usually be taken at any laboratory whose list of services includes vitamin D testing, or at an endocrinology center.
Preparation
There is no special, pre-planned preparation. The only thing to keep in mind is that the analysis is done on an empty stomach. You can eat in the evening, but in such a way that at least 8-12 hours pass between the procedure and the analysis. You cannot drink alcohol at least a week before the blood collection. You can stock up on chocolate in advance and eat it immediately after the procedure. This will improve your condition. You can drink sweet tea with sugar after the procedure.
Who to contact?
Technique for vitamin D testing
After the material is delivered to the laboratory, a study is conducted. The biological material is transferred to a centrifuge, coagulation factors are removed, thus obtaining pure serum. Then, further study of the obtained serum is conducted. The study can be carried out using different methods. Most often, liquid chromatography or immunochemiluminescent analysis are used. Most often, the second option is used, since it is more convenient to use, much easier and faster. From an economic point of view, it is also more profitable.
The principle of the method is to bind 25-hydroxycalciferol with paramagnetic particles coated with antibodies. After this, the particles are precipitated with a magnet and washed. A suspension is formed, to which polyclonal antibodies and various reagents are added. As a result, complexes are formed that have luminescent properties. Using special equipment, the intensity of luminescence can be assessed. Based on these data, the concentration of vitamin D is calculated.
Blood test for vitamin D
The procedure begins with taking blood from a vein. In compliance with all the rules of asepsis, venipuncture is performed, the required amount of blood is taken. The technique may vary slightly, depending on the method used. In most cases, blood is initially taken into a test tube containing EDTA. This is a gel that prevents blood from clotting and changing its properties. After the procedure is completed, the puncture site is pressed with a cotton ball, the arm is bent at the elbow and asked to hold it in this position until the bleeding stops completely.
Blood can be stored for some time in a special box, in a sealed tube. In this form it is usually transported to the laboratory. Blood is not frozen.
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Urine test for vitamin D
Vitamin D content is often tested using urine analysis. The Sulkovich test is used for determination. It allows one to determine the calcium content in the blood, on the basis of which further conclusions are made about the vitamin D content.
The results of the analysis are qualitative and are determined as follows: “-” indicates a deficiency of vitamin D, “+” or “++” indicates the norm, “+++” indicates excessive content.
Calcium and Vitamin D Analysis
Allows you to determine the presence of calcium in the urine. Based on this data, you can judge the characteristics of vitamin D metabolism. The study was called the Sulkovich test, or in full, the Sulkovich urine test. Provides information only on whether there is calcium in the urine. It is impossible to determine the amount of calcium excreted.
The analysis is especially important for children, since they have a high risk of abnormal development, rickets due to a lack of vitamin D and calcium metabolism disorders. If the child was born in winter or autumn, this risk increases due to a lack of sunlight. If a deficiency is detected, the vitamin must be added to the body artificially, and it is important to control the dosage. Deficiency entails bone disorders, decreased strength. Most often, these are the first signs of rickets. Subsequently, rickets manifests itself in the form of crooked legs, a disproportionately large head, and a forward-curved abdomen. Measures must be taken urgently, otherwise ossification of the skeleton will occur and the person will remain with such pathologies for life.
Excess calcium is also dangerous. Convulsive syndrome develops, aesthetic appearance is damaged. Excess calcium and vitamin are deposited in bones, as a result of which their growth slows down significantly.
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Analysis for vitamin D 3
The most accurate way to determine the vitamin D content is by the amount of vitamin D3 ( 25-hydroxyvitamin D3 ). Usually, a comprehensive study is conducted to determine this parameter. The fact is that the comprehensive analysis of "25 OH D3" implies a study of the two components of this vitamin - D2 and D3. The source of vitamin D2 is food, while the source of vitamin D3 is also ultraviolet rays. Blood serum is subject to study.
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Vitamin D absorption test
The most accurate picture describing the nature of vitamin D absorption in the body can be obtained by conducting a comprehensive blood test. For children, a urine test is sufficient.
Vitamin D test for a child
Children undergo urine testing to determine vitamin D. The method is simple and does not require any preliminary preparation. You only need to collect morning urine and take it for testing. Urine is collected in the morning, immediately after the child wakes up after a long sleep. This is done before the child starts drinking or eating. For small children, urine bags are used, which act as a reservoir for urine. Urine bags are disposable.
The technique of conducting the study is also not difficult. In the laboratory, urine is mixed with Sulkovich's reagent, which is a mixture of calcium salts and oxalic acid. As a result, turbidity occurs, the degree of which is used to judge the presence or absence of calcium in the urine. If this result does not fully clarify the clinical picture of the pathology, or it is insufficient for diagnosis or prognosis, daily urine is examined.
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Vitamin D test for adults
Adults are tested for vitamin D in venous blood. Simple laboratory equipment is used to detect the concentration of vitamin in blood serum. In adults, calcium metabolism disorders are fraught with numerous serious disorders. The main disorder is osteoporosis. In the body of an adult, vitamin D is involved not only in calcium metabolism, but also in phosphorus metabolism. As a result of deficiency, muscle weakness and tremor develop. The work of all internal organs, including kidneys and muscles, is disrupted. Regulation of blood pressure and normal heart activity are disrupted.
A normal amount of vitamin D is necessary for the proper functioning of the thyroid gland. The state of the immune system improves, blood clotting is normalized. The metabolism of other vitamins and microelements also depends on the normal content of vitamin D. With a low or excessive content of the vitamin, the functioning of the kidneys and liver may be disrupted.
One of the important properties is to ensure normal cell proliferation, which prevents uncontrolled cell division. Blocking uncontrolled cell proliferation is the key to successful treatment and prevention of oncological diseases. The immune system is also strengthened, resulting in the suppression of autoimmune diseases. This property ensures life extension in immunodeficiencies and AIDS.
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Vitamin D test when planning pregnancy
The analysis is mandatory for pregnant women, it is planned. This is due to the fact that this vitamin is very important for both the mother and the future child. It promotes normal calcium and phosphorus metabolism, regulates cell reproduction and division, their differentiation. It takes part in the synthesis of hormones. It mainly forms the skeleton of the future child. It prevents the development of varicose veins in the mother, maintains the beauty and health of hair, nails, teeth. With a lack of vitamin D in the body of a pregnant woman, a child may develop who will be prone to rickets. Usually, pregnant women, as well as during pregnancy planning, are prescribed vitamin D. Its exact concentration can only be determined with the help of analysis. The analysis is also needed to monitor these indicators in dynamics, since the amount of vitamin needs to be regulated in order to prevent either a deficiency or an overdose.
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How long does it take to test for vitamin D?
The analysis is done quite quickly. Usually it takes 1 working day, rarely – two. Many clinics immediately notify about the readiness of the results by phone or e-mail.
Normal performance
Normally, the concentration of vitamin D can vary within a fairly wide range: from 30 to 100 ng/ml. Values below 10 ng/ml indicate a deficiency of vitamin D, values above 100 ng/ml indicate an excessive content of vitamin D. This indicates possible intoxication of the body. Units of measurement may differ. If measurements were made in nmol/l, the normal values will be 75-250 nmol/l.
The device for analysis
There is a special device that allows you to conduct a comprehensive study of tissue density, calculate the content of calcium and vitamin D in the body. The procedure is called densitometry and is one of the varieties of X-ray examination.
Allows to quickly and effectively detect osteoporosis, determine the density of bone tissue as a whole, and each individual segment. This makes it possible to predict possible fractures, determine the risks of prognosis of existing fractures. Most often used for hip fractures, since this injury is very dangerous for life and health in old age. Research with this device is used in relation to women during menopause, especially if they are tall, with diabetes. It is also carried out if a person takes medications that promote the removal of calcium from the body.
Raising and lowering of values
If the values are higher than normal, the result is positive. This indicates an overdose of vitamin D and manifests itself as intoxication. Loss of appetite, vomiting, weakness occur. Sleep may be severely disrupted, and body temperature may increase.
If the values fall below the norm, the result is negative. This may indicate the development of such serious pathologies as liver cirrhosis, renal failure, osteitis, thyrotoxicosis, intestinal inflammation, rickets. Also, the content of vitamin D can decrease as a result of taking certain medications, such as anticonvulsants, glucocorticosteroids. The analysis for vitamin D can be negative during pregnancy and lactation.