Many men are now self-injecting testosterone cypionate as part of their HRT program and find themselves, for one reason or another, with expired vials. And they wonder if it is safe to use this “old” testosterone cypionate. Of course, I encourage men to play it safe and go by the expiration date for a variety of reasons:
1. Lack of Preservatives. Cypionate from one of the bigger pharmaceutical manfacturers will tend to have a pretty long expiration date. However, some of the compounding pharmacies’ expiration will be much shorter and this is for a variety of reasons. One of them is that, at times, they deliberately do not put preservatives in their preparations. Regardless, it is best to play it safe and respect their judgement as to how long they think their preservative, or lack thereof, will last.
2. Oil Breakdown. Testosterone cypionate is in an oil base and, while the ester itself is very stable, the oil itself can break down even more quickly. Only the manufacturer knows the shelf life of their oil preparation and so it is best to heed their analysis. For example, some will be stored in sesame or cottonseed oil. And castor oil will, I believe, last even longer.  Again, only the manufacturer knows all the details of their oil product.
NOTE: It is possible, although rare, to have an allergic reaction to the oil itself. Discuss with your doctor if you think this an issue for you.
I know everyone is trying to save a few dollars and manage their money wisely. But, when it comes to medications, this is not a good idea. I have read stories of men injecting from old vials and finding that it actually hurt. Cypionate is just not that expensive. Why risk it? Just get a new prescription and play it safe.
1) Clin Interv Aging, 2007 December, 2(4):577 590, “Testosterone depot injection in male hypogonadism: a critical appraisal”