The Merck Serono New Fertility Pen 2.0 pen injector is used in hormone therapy for women undergoing fertility treatment, supporting their family planning. The pen is designed in such a way that each dose may be individually set and easily identified through a dose window. If the dose has not been completely administered, then the missing amount is immediately displayed, thereby reducing the risk of dosing errors. This provides the user of the pen with reassurance and confidence.