If you lost your MitID you must block it.
Help at Citizen Service
If you need help at Citizen Service to get your MitID, remember to book an appointment before you show up at a Citizen Service Center. On borger.dk, you can both find your local Citizen Service and schedule an appointment. It is important that you bring valid identification, such as a passport or driver's license, so that Citizen Service can confirm your identity.
Have a spare MitID
It is a good idea always to have a spare MitID. Then you can still use MitID if you e.g. should lose your phone with the MitID app.