Are there any downsides to taking vitamin D3?
                                
                                
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                                    4 min read                                
                            
                                According to the NIH, while beneficial, very high levels of vitamin D in the blood (over 150 ng/mL or 375 nmol/L) can be harmful and, in rare cases, even fatal. Taking excessive amounts of vitamin D3 supplements can lead to a condition known as vitamin D toxicity, which is primarily caused by an overaccumulation of the fat-soluble vitamin in the body over time.