Hello, gentlemen! 

Huge thanks to our client who asked a question about crystallization and suggested the idea of writing this article. We hope the info will be useful! 

It’s really rare but sometimes in vials, you can see inhomogeneities in the oil or it could be a hard layer floating on it.

It's crystallization of active ingredient in this particular case – Testosterone. "Long" esters of Testosterone like Cypionate and Undecanoate have a tendency to crystallize.

When preparing the product, it is important not only the presence of carrier oil but also substances that improve solubility and sterile properties are added to the composition. Then the high temperature contributes to the complete dissolution of the active substance.

Based on this, it is clear that lowering the temperature can contribute to the crystallization of the product. With our products it's rare, but possible.


Crystallization is a normal phenomenon for pharmaceutical preparations. The medical instructions for Retabolil, Testosterone Cypionate, and Undecanoate directly indicate that in the event of crystallization, the ampoule should be heated until the inhomogeneities disappear.

But the Pfizer company conducted a separate investigation and released a report on it, excerpts from which we will give below. A link to the full version of the report is also attached.

«...The high concentration of active ingredients makes the product very susceptible to crystallization when exposed to a temperature lower than recommended on the label [20°C to 25°C (68°F to 77°F)]. This product attribute is well known and is specifically addressed with instructions in both the USPI and on the product vial label.

Potency testing from these lots confirms two key product quality attributes:

  • The product can be warmed, shaken, and the crystals re-dissolved, when prepared according to instructions found in the product insert and on the vial label; and,
  • The potency of the retain and complaint samples confirm product potency at the labeled strength (200 mg/mL). Based on our testing of and a medical and safety evaluation, all distributed lots of Depo®-Testosterone 200 mg/mL continue to be acceptable for use, regardless of the presence of crystals, when used as directed in the product insert.»

https://pfe-pfizercom-prod.s3.amazonaws.com/products/hcp_depotestosterone.pdf

! So thus, crystallization does not affect the quality of the product in any way, and this has been proven by an official investigation and confirmed by a qualified commission. Its important to know!

Also, please note, if there is no crystallization at any temperatures, it may be not so good too. If there are aggressive solvents in the chemical composition (often used in cheap products), then crystallization does not happen even in cold, however, this makes the liquid more irritating to human tissues, so systemic inflammation and pips are highly possible, and we, as bona fide manufacturers, avoid it.

So what should you do?

✅ Should this happen, place the vial in a container of hot water, shaking occasionally, until the crystals dissolve.

✅ Warm some water in your microwave. Sit the vial halfway in the hot water, wait 30 seconds shake the vial a little, and repeat with hotter water till the crystals are gone.

If water did not help dissolve, then:

✅ You can put the vial on the pan and slowly heat it until the crystals are completely dissolved. It can take up to 10-15 minutes as practice shows.

Even if we use heat-resistant medical glass, so the likelihood that the vial will burst due to temperature changes is very low, avoid sudden temperature changes.

! Important: after this, the oil must be cooled to a temperature of 38 degrees before injecting

Thank you for your attention and support, Gentlemen!