Type of test Blood

Normal findings

Total 25-hydroxy D (D2 + D3 ): 25-80 ng/mL 1,25(OH)2 D

Males: 18-64 pg/mL

Females: 18-78 pg/mL

Test explanation and related physiology

Vitamin D levels are calculated to ensure that postmenopausal women have adequate vitamin D levels to absorb dietary calcium. Vitamin D is a fat-soluble vitamin. The two major forms of vitamin D are vitamin D2 (or ergocalciferol) and vitamin D3 (or cholecalciferol). Vitamin D2 is provided by dietary sources. Because only fish is naturally rich in vitamin D, most of the vitamin D2 intake in the industrialized world is from fortified products, including milk, and breakfast cereals or supplements.

Vitamin D3 is produced in skin exposed to sunlight, specifically ultraviolet B (UVB) radiation. In this scenario, 7-dehydrocholesterol reacts with UVB light at wavelengths between 270 nm and 300 nm to produce vitamin D3 .

After vitamin D is produced in the skin or consumed in food, it is converted in the liver and kidney to form 1,25- dihydroxy- vitamin D (1,25[OH]2 D), the physiologically active form of vitamin D. After this conversion, the hormonally active form of vitamin D is released into the circulation. Vitamin D regulates the calcium and phosphorus levels in the blood by promoting their absorption from food in the intestines and by promoting reabsorption of calcium in the kidneys. This enables normal mineralization of bone needed for bone growth and bone remodeling. Vitamin D inhibits parathyroid hormone secretion from the parathyroid gland.

Vitamin D deficiency can result from inadequate dietary intake, inadequate sunlight exposure, malabsorption syndromes, liver or kidney disorders, or by a number of metabolic hereditary disorders. Deficiency results in impaired bone mineralization and leads to bone-softening diseases.

Vitamin D levels can be measured in the blood. Usually 25-hydroxy vitamin D2 and D3 are measured and added to obtain the total 25-hydroxy vitamin D level. They are usually reported individually and as a total. Therapy is based on the measurement of total 25-hydroxy vitamin D levels. 1,25-dihydroxyvitamin D (the active metabolite of vitamin D) can be measured and is helpful in patients who have signs of vitamin D deficiency yet have normal levels of total vitamin D.

Interfering factors

* Corticosteroid drugs can decrease vitamin D levels by reducing calcium absorption.

* The weight-loss drug orlistat and the cholesterol-lowering drug cholestyramine can decrease vitamin D levels by reducing the absorption of vitamin D and other fat-soluble vitamins.

* Barbiturates and phenytoin decrease levels by increasing hepatic metabolism of vitamin D.

 Procedure and patient care

• See inside front cover for Routine Blood Testing.

• Fasting: no

• Blood tube commonly used: red or green If the patient has a vitamin D deficiency, educate him or her about dietary sources and the need for sunlight.

Abnormal findings

 Increased levels

- Williams syndrome

- Excess dietary supplements

Decreased levels

- Rickets

- Osteomalacia

- Osteoporosis

- Gastrointestinal malabsorption syndromes

- Renal failure

- Liver disease

- Familial hypophosphatemic rickets

- Acute inflammatory disease

- Inadequate dietary intake

- Inadequate exposure to sunlight

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم العلاقات العامة يسلم دعوة الملتقى التربوي التنسيقي الثاني لتربية محافظة ذي قار

شعبة فاطمة بنت أسد تجري الاختبارات النهائية للمشاركات في دورة هدى للناس

قسم الشؤون الفكرية يصدر الجزأين الأول والثاني من سلسلة تاريخ الاستعمار

جمعت بين الدقة والجمال.. متحف الكفيل يضم سجادة نادرة تعود لأكثر من ثمانية عقود

المزيد

الآخبار الصحية

عناصر منزلية قد تؤثر على الخصوبة وفرص الحمل

شكل الدماغ قد يتنبأ بخطر الخرف قبل سنوات

طريقة صينية بسيطة للوقاية من السكري

هل تساعد المانغو في الوقاية من السكري؟

المزيد

الآخبار التكنلوجية

رقم غامض ولا إنترنت.. متوجون بنوبل للطب لم يعلموا بفوزهم

"سيري" تحت المجهر.. تحقيق فرنسي جديد ضد شركة "آبل"

أميركيان وياباني يفوزون بجائزة نوبل للطب

تحول غير مسبوق.. إنستغرام تمنح مفاتيحها للمستخدمين

المزيد

مواضيع ذات صلة

white blood cell scan (WBC scan, Inflammatory scan)

white blood cell count and differential count (WBC and differential, Leukocyte count)

Basal Hormone Measurements of Testis

vitamin B12 (Cyanocobalamin and methylmalonic acid [MMA])

virus testing

viral cultures

Laboratory Investigations of Pheochromocytoma and Paraganglioma

varicella virus testing (Antibody testing for Varicella zoster virus, Varicella zoster virus [VZV], Herpes virus-3)

uroporphyrinogen-1-synthase

urine culture and sensitivity (C&S)

uric acid, blood, and urine

urea breath test (UBT, Helicobacter pylori breath test)