Please remember to inform your supervisor about absencies due to sickness. You should also send an e-mail to henkilosto@cs.helsinki.fi for hour allocation purposes.
You should also immediately fill in the form in SAP HR: https://flamma.helsinki.fi/portal/home/sisalto?_nfpb=true&_pageLabel=pp_list&placeId=HY274133

For shorter sick leaves (1-3 days), you don't need a medical certificate from a doctor or nurse. If your absence lasts for 4-5 days, you need a nurse's or doctor's certificate. If your absence last over 5 days, you will need a medical certificate from a doctor. Go to Mehiläinen or your local healthcare centre for the certificate.