Brief Answer:
Not to use any medication after its expiry date.

Detailed Answer:
Hi
Welcome to HCM.
I have gone through your query.

I encourage you to play it safe and go by the expiration date for a variety of reasons:
1. Preservative -- it is bettet to respect the judgement of manufacturer as to how long they think their preservative 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.
3. Loss of Efficacy -- testosterone cypionate is a stable molecule. Furthermore, hormones do not tend to break down into harmful byproducts. But, that said, any loss of efficacy is not good for your testosterone therapy.

In a nutshell, I would not suggest you to use any medication after its expiry date.

Hope this helps.
Take care.

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