I have diphtheria, how long until I can return to work?

Expert link. Here's a link which should help you: http://www.Ncbi.Nlm.Nih.Gov/pubmedhealth/pmh0002575/.
Doctor's orders. There are many potential complications to diphtheria and the recovery is slow. The most common complication is inflammation of the heart muscle (myocarditis). The nervous system is also frequently and severely affected, which may result in temporary paralysis. The diphtheria toxin can also damage the kidneys. You should be under the constant care of a physician.