Vitamin D testing and the use of vitamin D supplements have increased substantially in recent years. Currently, the role of vitamin D supplementation, and the optimal vitamin D dose and status, is a subject of debate, because large interventional studies have been unable to show a clear benefit (in mostly vitamin D replete populations). This may be attributed to limitations in trial design, as most studies did not meet the basic requirements of a nutrient intervention study, including vitamin Dreplete populations, too small sample sizes, and inconsistent intervention methods regarding dose and metabolites. . Methods: Research approach: Quantitative approach, Sampling technique: Probability Convenient Sampling Technique. Research Design: Pre experimental one group pretest & posttest design. The present study was conducted in olapalayam at Namakkal District, Tamilnadu. The participants are adults from olapalayam. The total participants of 50 adults were from olapalayam at Namakkal district. Results: The level of knowledge among adults in pretest, among the adults 32(64%) of them had inadequate knowledge, 16(32%) of them had moderate knowledge and 2(4%) in adequate knowledge regarding Hypovitaminosis. During the level of knowledge among adults in post-test, among the adults, none of them had inadequate knowledge in posttest, 14(28%) of them had moderate knowledge and 36 (72%) of them adequate knowledge regarding Hypovitaminosis. During pretest mean value was 15.46 and standard deviation was 3.98, in posttest mean value was 22.31 and standard deviation was 43.32. The calculated value of t was 8.42 which is greater than table value, it is noted that there was a highly significant between pre and post test score, so there is effectiveness on structured teaching problem regarding Hypovitaminosis. It shows that, association between level of knowledge with selected demographic variables for considering the variables age, education status, occupation, dietary pattern, work, knowledge regarding Hypovitaminosis (D), exposure of sunlight had no association between levels of knowledge, type of residence, sunlight knowledge about vitamin D had association with level of knowledge. The Chi – square values as followed: Chi – square value of age in years was 3.13 (Df = 6, NS).Chi – square value of educational status was 4.19 (DF = 6, NS)Chi – square value of residence was 6.89 (DF = 2, NS)Chi – square value of occupation 1.36 (DF = 2, NS)Chi – square value of dietary pattern was 3.56 (DF = 2, NS)Chi – square value of types of work was 1.83 (DF = 2, NS)Chi – square value of knowledge regarding Hypovitaminosis (D) was 1.83 (DF = 2, NS)Chi – square value of how got knowledge of Hypovitaminosis (D) was 1.83 (DF = 2, NS)Chi – square value of exposure of sunlight was 4.13 (DF = 2, NS)Chi – square value of sunlight can give Vitamin D was 8.43 (DF = 2, NS)