Eevated Vitamin D Blood LevelsA healthcare provider can order a blood test to check your vitamin D level. Experts do not believe that excessive sun exposure results in vitamin D toxicity due to how sunlight activates different forms of vitamin D in the skin. Vitamin D toxicity is rare, and most cases of vitamin D toxicity are caused by inappropriate supplement dosing and prescription errors. For example, a review of case reports of vitamin D toxicity found that many resulted in the overcorrection of vitamin D deficiency. Possible Vitamin D Side EffectsGenerally, eating foods rich in vitamin D is well tolerated, and there are no known side effects from vitamin D produced by sunlight exposure.