Vitamin-D: Introduction, Normal Range in Blood, Daily Requirement, Clinical Significance, Symptoms, and Keynotes

Introduction of Vitamin-D

Vitamin D is not a vitamin but a hormone or prohormone that is essential for maintaining healthy bones and teeth. It also helps in regulating inflammation, immune function, intestinal calcium absorption, and maintaining adequate blood levels of calcium and phosphorus, which are necessary for healthy bone mineralization. Its deficiency in children can cause rickets (softening of the bones), while in adults, vitamin D deficiency manifests as osteomalacia (poor bone density and muscular weakness). Its long-term deficiency can also present as osteoporosis.

Vitamin-D: Introduction, Normal Range in Blood, Daily Requirement, Clinical Significance, Symptoms, and Keynotes
Fig. Collecting Blood for Vitamin-D Test

Vitamin-D Range in Blood

Test ResultLevel
≤12 ng/ml (30 nmol)Low (may cause rickets and osteomalacia)
≥20 ng/ml (50 nmol/l)Adequate
≥50 ng/ml (125 nmol/l)High (linked to potential adverse effects)
< 30 ng/mLVitamin D deficiency (inadequate for bone and overall health in healthy individuals in the range of 12 to <20 ng/mL)
20 to 30 ng/mLInsufficiency
Fig. Ranges of Vitamin D in our blood

Daily Requirement of Vitamin-D

Age-wise requirements of vitamin D should be taken at a maximum level per day are given as follows-

Age Upper Limit
Up to 6 Months25 mcg (1000 IU)
7 to 12 months38 mcg(1500 IU)
1 to 3 years63 mcg (2500 IU)
4 to 8 years75 mcg (3000 IU)
≥9 years100 mcg (4000 IU)
Table: Age-wise requirement of Vitamin D per day

Clinical Significance of Vitamin-D

The level of vitamin D in the blood is more than normal, the condition is called hypervitaminosis D which can cause abnormally high levels of calcium in the blood and may affect bones, tissues, and other organs causing high blood pressure, bone loss, and kidney damage if not treated.

The level of vitamin D in the blood is less than normal, the condition is called hypovitaminosis D or insufficiency or deficiency of vitamin D that may develop soft, weak, or brittle bones leading to rickets in children, or osteomalacia and osteoporosis in adults. Low vitamin D may also affect the health of muscles, nerves, the brain, and the immune system.

Vitamin-D Test-Normal Range, Unit, Testing Method and Clinical Significance
Fig. Vitamin-D Test-Normal Range, Unit, Testing Method and Clinical Significance

Symptoms of Vitamin-D

Numerous people having vitamin D deficiency do not show any symptoms. However, a chronic deficiency may cause primary conditions like

  • hypocalcemia (calcium deficiency disease) and
  • hyperparathyroidism (parathyroid glands create a hormone imbalance that raises the blood calcium levels)

If these conditions are not controlled, secondary symptoms will arise like-

  • bone fragility (mainly in older adults)
  • bone pain
  • osteoporosis
  • fatigue
  • muscle twitching
  • muscle weakness
  • myalgia (muscle aches and pain)
  • arthralgia/joint stiffness (joint pain)

If hypovitaminosis D occurs for a prolonged time, it may create complications as shown below-

  • Cardiovascular problems
  • Autoimmune disorders
  • Neurological diseases
  • Infections
  • pregnancy complications
  • Certain cancers e.g. breast, prostate, and colon cancer

Maintenance of Vitamin D-level

Increase vitamin D levels by doing the following activities-

  • Regular Sunbathing for 10-15 minutes.
  • spend more time outdoors who live in colder climates, or who spend most of their time indoors.
  • Maintain food sources of vitamin D in your diet like oily fish, beef liver, portobello mushrooms, chicken breasts, dairy products, and fortified cereals.

Keynotes on Vitamin-D

  • A blood sample is needed for testing Vitamin-D levels.
  • Vitamin D is also referred to as “calciferol”.
  • Vitamin D deficiency is called so when the level of 25-hydroxyvitamin (25 OH D) is less than 30 ng/mL.
  • A serum concentration of 25(OH)D is the main indicator of vitamin D condition.
  • Vitamin D supplements are available in strengths of 1000 IU, 2000 IU, 5000 IU, and 50,000 IU.
  • Concentrations higher than 150 ng/mL (325 nmoL/L) may result in vitamin D intoxication and are associated with hypercalcemia and such a case is extremely rare.
  • Vitamin D is found in oily fish (e.g. salmon, mackerel, sardines, tuna, and trout), milk and orange juice, and some bread and cereals.
  • Recurrent vomiting, polyuria, confusion, polydipsia, apathy, abdominal pain, and dehydration are the symptoms of vitamin D toxicity.
  • Vitamin D has D2 (ergocalciferol) and D3 (cholecalciferol) forms in foods and dietary supplements.
  • 25-hydroxyvitamin D [25(OH)D] is also known as “calcidiol while physiologically active 1,25-dihydroxy vitamin D [1,25(OH)2D] as “calcitriol”.
  • Serum concentrations of Vitamin D or 25(OH)D are reported in both nanomoles per liter (nmol/L) and nanograms per milliliter (ng/mL).
  • 1 ng/mL is equal to 2.5 nmol/L.

Further Reading


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