Each 80mcg pen, if fully injected, is good for 30 days, although there was always a bit left in the pen at the end of that time period. I always injected in my belly, rotating the area. I did encounter increased belly fat with Tymlos but I had a 15% gain in my spine and 3.5% in my hips after 2 years, so I’ll deal with the extra fat for now. I finished my protocol in June and the belly fat is still there. Hoping it decreases as time goes on. With osteo and the med choices, there are positives and negatives. This journey is full of decisions and we do the best we can with what we are given. Every drug comes with potential side effects. We are all different and if a med causes a side effect, we have to weigh the risks versus the benefits. I’m glad I stuck with the full 2-year protocol. Wishing you a positive experience. 🌹