Vitamin D deficiency is more prevalent in Iran, making the rational use of it more critical. To this end, assessing people’s knowledge about the rational use of vitamin D and its safety is worthwhile to pursue. Objectives: This study aims to evaluate the level of consumers’ knowledge about vitamin D and its relationship with serum levels. Methods: This is a cross-sectional survey designed to assess consumers’ knowledge and its association with demographic characteristics and their serum 25-hydroxy vitamin D3 (25(OH)D) levels in community pharmacies. The association between demographic parameters, lifestyle, habits, and serum levels was reported. Results: 384 individuals participated in this study, among whom 345 (89.8%) consumers requested large doses of vitamin D3. The average knowledge score was 23.67 ± 7.76 out of 50. The average serum level of 25(OH)D was reported as 49.01 ± 32.01 ng/ml, resulting in 117 (30.5%) subjects were in the "insufficient" levels, 223 (58.1%) were in the "sufficient”, and 44 (11.5%) were in the "hypervitaminosis" levels. There is a significant inverse association between knowledge and age, weight, body mass index, education levels, serum level, and monthly dose. Also, a significant inverse association was detected between knowledge in terms of toxicity and vitamin D level. Further, participants’ knowledge of "hypervitaminosis" was lower than those with "sufficient" levels. Conclusion: Although almost all consumers had a sufficient level of 25(OH)D, the lack of knowledge about vitamin D was evident. It could lead the people being exposed to hypervitaminosis, as were seen in 11.5% of the participants.Background: Vitamin D deficiency is more prevalent in Iran, making the rational use of it more critical. To this end, assessing people’s knowledge about the rational use of vitamin D and its safety is worthwhile to pursue. Objectives: This study aims to evaluate the level of consumers’ knowledge about vitamin D and its relationship with serum levels. Methods: This is a cross-sectional survey designed to assess consumers’ knowledge and its association with demographic characteristics and their serum 25-hydroxy vitamin D3 (25(OH)D) levels in community pharmacies. The association between demographic parameters, lifestyle, habits, and serum levels was reported. Results: 384 individuals participated in this study, among whom 345 (89.8%) consumers requested large doses of vitamin D3. The average knowledge score was 23.67 ± 7.76 out of 50. The average serum level of 25(OH)D was reported as 49.01 ± 32.01 ng/ml, resulting in 117 (30.5%) subjects were in the "insufficient" levels, 223 (58.1%) were in the "sufficient”, and 44 (11.5%) were in the "hypervitaminosis" levels. There is a significant inverse association between knowledge and age, weight, body mass index, education levels, serum level, and monthly dose. Also, a significant inverse association was detected between knowledge in terms of toxicity and vitamin D level. Further, participants’ knowledge of "hypervitaminosis" was lower than those with "sufficient" levels. Conclusion: Although almost all consumers had a sufficient level of 25(OH)D, the lack of knowledge about vitamin D was evident. It could lead the people being exposed to hypervitaminosis, as were seen in 11.5% of the participants.

Individuals over 18 years’ old who requested vitamin D and had taken vitamin D regularly in the past two months were invited to participate in this study, whether or not this request was based on a prescription. The logic behind this lag time is that some scholars argue that it takes about 6-12 weeks for this vitamin to reach a steady state in the body (19). The available pharmaceutical dosage forms include soft gels containing 50,000 international units (IU), tablets, soft gels containing 1000 and 2000 IU, and ampoules containing 300,000 IU. If the participants met eligibility criteria, a questionnaire was filled out by phone call. The patient was invited to determine the vitamin D level in the specified laboratories.