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Document and Entity Information
12 Months Ended
Dec. 31, 2021
Document and Entity Information [Abstract]  
Document Type 6-K
Document Period End Date Dec. 31, 2021
Entity Registrant Name Genmab A/S
Entity Central Index Key 0001434265
Current Fiscal Year End Date --12-31
Document Fiscal Year Focus 2021
Document Fiscal Period Focus FY
Amendment Flag false