If you register as a Ukrainian refugee upon arrival and apply to receive social assistance (Sozialhilfe in German), you will receive a health insurance card from a state-run health insurance fund. This allows you to access healthcare services and most doctors free of charge. The costs will be covered by the welfare office of the German government (Sozialamt in German).
If you are not yet registered as a refugee from Ukraine, a doctor issues a bill which you would have to pay from your pocket.
When it comes to medicine, you usually need to pay an additional amount for your prescription drugs at the pharmacy. This additional payment is usually between 5 euros – maximum 10 euros.
You cannot claim welfare incl. medical benefits in Germany by using your Ukrainian health insurance. According to the rules, you have to be in the German insurance system in order to receive financial support from the German state.