Vitamin D3 is a fat-soluble secosteroid synthesized in the human skin upon exposure to ultraviolet B (UVB) radiation from sunlight and is also derived from dietary sources such as fatty fish, liver, egg yolks, and fortified dairy products [1]. The biologically active form, calcitriol (1,25-dihydroxyvitamin D), plays a vital role in maintaining calcium and phosphate balance for bone formation and remodeling [2]. Recent decades have witnessed an expansion in the understanding of Vitamin D3’s extra-skeletal functions, particularly in modulating immune, cardiovascular, endocrine, and neurological systems [3]. Despite this, Vitamin D3 deficiency remains a widespread and underdiagnosed condition globally. According to the World Health Organization and various epidemiological studies, over one billion individuals worldwide suffer from suboptimal Vitamin D3 levels [4,5]. A variety of environmental and physiologic factors are associated with hypovitaminosis D, such as geographical latitude, decreased availability of sunlight, higher skin melanin content, older age, obesity, and malabsorptive syndromes [6–8]. To the significance, indoor lifestyle behaviors and sunscreens have also limited the dermal synthesis of cholecalciferol [9]. Also, some chronic diseases, like chronic kidney disease [10], liver diseases [11] and disease of the stomach and intestines [11,12], reduce the metabolism and absorption of Vitamin D3. Deficient vitamin D exists globally and it is a paramount public health problem in India and it has been roughly calculated that 490 million beings are deficient to vitamin D in India.[13-15] Recent systematic review has demonstrated that almost one out of three of all the studies conducted globally has found vitamin D deficiency. In India vitamin D deficiency has been found to be prevalent in approximately 7090% over all ages from children to adult.  Manoharan et al in his study had shown that vitamin D deficiency prevalence was 40.2% in the group of adult patients with complaints of non-specific musculoskeletal pain attending orthopaedic department. [16,17] Present study was done to check Vitamin D3 levels and its Deficiency.

The descriptive type cross-sectional study was done in the patients attending outpatient clinic . Duration of the study was one year from with sample size of 80 study participants. Informed written consent was obtained in local language from all the study population registered in the study.

Patients with age group between 25 and 70 years of both genders with  illness attending orthopedic  and Medicine outpatient department were included in the study. Patient of more than 70 years and less than 25 years, pregnant and lactating mother, patients with dermatological disorder, chronic liver disease, chronic kidney disease,  parathyroid disease, patients on chronic drug therapy like anticonvulsants, antitubercular drugs that may affect the metabolism of vitamin D and patient on vitamin D supplementation and patients using sunscreens were eliminated from this study.  Routine blood investigations and specific laboratory investigations like level of serum 25 hydroxy cholecalciferol was done and the reports were recorded in a data collection sheet. Biological reference value of serum 25 hydroxy cholecalciferol based on endocrine society guidelines are <20 ng/ml, 21-29 ng/ml, 30-100 ng/ml were considered as deficient, insufficient, sufficient respectively.[3]  Symptoms related to vitamin D3 were noted in each subject. The data collected were tabulated and statistically analysed. The most common method for measuring Vitamin D3 levels in biochemistry is the 25-hydroxyvitamin D (25(OH)D) test, which is a blood test. This test measures the primary circulating form of vitamin D in the body. While other forms of vitamin D exist (like vitamin D2 and the bioactive 1,25-dihydroxyvitamin D), 25(OH)D is the most reliable indicator of overall vitamin D status. 

1. Sample Collection: A blood sample is typically drawn via venipuncture, usually from a vein in the arm. The blood is collected into a tube and allowed to clot, after which the serum is separated.  Special handling is often required to protect the sample from light and extreme temperatures. 
2. Testing Methods:

Immunoassays: These are commonly used in clinical laboratoriesThey are relatively fast and cost-effective, but can sometimes have cross-reactivity issues with other vitamin D metabolites. 

Table 1: Serum Vitamin D3 levels in subjects.

Table 2 : Symptoms in Vitamin D3 Deficiency subjects

Table 1 shows 45% subjects were having Insufficient (20-30ng/ml) Vitamin D3 levels. 40% subjects were Deficient (<20ng/ml). 15% subjects had Sufficient (>30 ng/ml) Vitamin D3 levels.

Table 2 shows Symptoms in Vitamin D3 Deficiency subjects, most common symptoms were fatigue, bone pain ,joint pain, muscle weakness. Other symptoms were  Weak immunity (recurrent infections), Mood changes, Depression, hair loss.

The report of different studies had demonstrated that deficiency in Vitamin D in every race, all age groups and various ethnic backgrounds.[17] It is estimated that deficiency to vitamin D influence greater than one billion people globally and it is endemic in India. India is a nation of ample sunlight but astonishingly found to have numerous people with vitamin D deficiency regardless of their place they live.[18]

Vitamin D deficiency affects more than 50% of the population worldwide and the main factor is the change in our lifestyle. With change in the working environments our exposure to sunlight is reduced which is the main component required for ultraviolet B rays to induce the Vitamin D production in the skin [19]. Vitamin D performs various functions in the body such as increase in calcium absorption, increase insulin secretion, increase in bone formation and increase in cell differentiation. 

Vitamin D is available in two different forms. First is Vitamin D3 also called as Cholecalciferol and second is Vitamin D2 also called as Ergocalciferol. Vitamin D3 is a natural occurring form and produced in skin cells from 7dehydrocholesterol (7-DHC) underneath the ultraviolet (UV) light and vitamin D2 is produced from the natural sterol, i.e., ergosterol. The complete metabolism of Vitamin D3 is discussed in detail elsewhere [20,21].The deficiency of Vitamin D in the body (a condition known as hypovitaminosis D) affects various body parts which ultimately lead to rickets, cancer, heart diseases, type 2 diabetes, falls and fractures, auto-immune disease, and depression . With ageing the skin is not able to synthesize sufficient Vitamin D, there is change in lifestyle, obesity and eating habits too. These all leads to reduction in mineral density, weakness, osteoporosis, musculoskeletal pain, risk of fractures and falls in adults and rickets in children [22].   Numerous sources rich in Vitamin D are available. These are rich diet sources (natural and animal sources), direct sunlight exposure and vitamin D supplements for maintenance of its status in the body.

Vitamin D rich diet sources: Vitamin D can be obtained from both natural as well as animal sources. Natural sources are milk (Almond and Cow), cheese, breads, fruit juices, fruits (raspberries, blueberries, and pomegranates), and yogurts while animal sources are salmon and mackerel fish as well as cod liver oil. Mushroom is also one of the rich sources of vitamin D2 [23].  Sunlight Exposure: Vitamin D is also called as sunshine vitamin because direct sunlight exposure lead to vitamin D production in the skin cell and it is a natural ways to prevent its deficiency. However, numerous factors such as age, sunscreen use, duration of sunlight exposure, skin pigmentation, latitude, zenith angle of sun, head covering and cloth length or as per the religious culture and customs, etc., influences the production of Vitamin D in skin [24,25]  Vitamin D supplements: Vitamin D is obtained from supplements available in the market. These multivitamins generally contain 400 IU, 800 IU and 1000 IU of vitamin D but nowadays various supplements containing only vitamin D are available in different IU, such as 400 IU, 1000 IU, 2000 IU, 4000 IU, 5000 IU, and 50000 IU vitamin D3 [26]. Sunlight help the skin to produce sufficient vitamin D which is required for bone formation, muscle strengthening, reduction in inflammation, immunity boost up, protection against skin cancer. Daily exposure to direct sunlight for about 15-30 minutes for twice a week is very helpful in vitamin D production but without the application of sunscreen. Because the sun protection factor (SPF) present in these sunscreen block the capability of the skin to absorb UV B rays which are going to affect the production of vitamin D [27]

At the present time vitamin D deficiency is one of the most common health problems in the world. As a matter of fact vitamin D deficiency is pandemic worldwide. In this study there is greater prevalence of deficient and insufficient status of vitamin D in people of all ages. Aggressive screening along with treatment strategies may prevent vitamin D deficiency and insufficiency.

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