Usually on a slin pin, each 10th mark represents 100mcg, which means the 10th mark itself represents 1mg or 1ml.
Now, in most cases, HGH is mixed with 1ml of solution, or 1000mcg. Again, in most cases this will represent 10iu of HGH. So in your case, odds are that each increment on these preloaded syringes represents 1iu of HGH.
Arnold JR, you generally give what seems like really good information, but I've got to step in here because the way I read what you posted it is very, very wrong.
There are two types of insulin syringes available on the market---U100 (which is human/veterinary use) and U-40, which is only veterinary use. The syringes are based on a 1ml maximum content in which a U100 insulin syringe has 100 units of insulin per 1 ml. Obviously U40 syringes have 40 units of insulin per 1 ml--- and as a result, markings on a syringe that result in roughly 2.5 times as much volume per unit when comparing a U100 to a U40 syringe. As a general rule, you cannot get U40 syringes from a human pharmacy (they again are veterinary use, there is no longer any U40 human insulin available on the market that I'm aware of) however you can get U40 or U100 from a veterinary supplier because of the crossover of insulin from human to veterinary medicine. Now to complicate things a bit more, U100 insulin syringes are available in 1/3, 1/2, and 1 ml size syringes. U40 syringes are typically only available as 1/2 and 1 ml syringes. On insulin syringes, each individual mark represents 1 Unit---and the marks are based on if its U40 or U100 insulin with the syringes clearly labeled as U40 or U100.
Also remember that Insulin Units (U-40 or U-100) are different from International Units (IU). An IU is a measure of biological activity---in insulin 1 IU of insulin has the biological equivalent of about 45.5 μg pure crystalline insulin. Use of IU to measure insuling makes things even more confusing becuase you aren't measuring volume, you are measuring biological activity. I personally try to not think about IU of insulin unless I want to torture myself.
All of that sad, a 1 ml (or CC) U100 insulin syringe IS NOT the same as a 1 ml (or 1 CC) tuberculin syringe---which is divided from 1 ml into 0.01ml segments (one 1/100th of a CC) so that each mark represents 0.01 ml. To the casual observer, the measurements of 0.01 ml and 1 U of insulin appear to be the same, but they aren't. We did a study a while back on measuring the mass of insulin given out of a TB syringe vs a U100 insulin syringe in birds. The tuberculin syringes consistantly had variable dosing volumes/masses. The best reason we could figure was due to the subtle difference between 1 U of U100 insulin and the differences in hub size. A typical TB syringe has approximately 0.03 to 0.06 ml of fluid left in the hub, while an insulin syringe has less than 0.005 ml. If you depress the syringe hard enough to compress the rubber plunger, you will inject a portion of that hub fluid using a tuberculin syringe. You'll only get a negligable amount (ie a tiny, tiny drop) out of an insulin syringe. If you don't depress the plunger that hard, obviously you won't inject it. This isn't a big deal when administering BPD or PPD or antibiotics from a TB syringe but can be a huge issue if you are administering something as sensitive as insulin to a child or small animal---something where a 0.06 ml difference in volume injected may result in hypoglycemia.
With GH--the only product I have any experience with is the use of Humatrop in a german shepard dog that had a congenital defect in GH production. This dog wasn't a patient of mine, but the case was discussed in quite a bit of detail at the hospital. Humatrop at that time was only available as a 5 mg vial. This 5 mg vial contained the 15 IU of biologically active somatropin (growth hormone)---remember again an IU is a measure of biologicaly activity, not a measure of volume or mass. It was to be reconstituted with the 5 ml vial of sterile water which was supplied. This resulted in a diluted concentration of 1 mg/ml of somatropin (concentration of base product/concentration of dilulent= final concentration). This 1 mg/ml of somatropin resulted in a 3 IU/ml concentration of somatropin (or 3 IU/ml of biologically available growth hormone). If a tuberculin syringe would be used to inject it like we did with this dog, 0.01 ml (1 mark on the syringe) was the equivilant of 0.01 mg of growth hormone which was the equivilant of 0.03IU of growth hormone---if I didn't mess up the math with the conversions. Again, if I want to torture myself, I do calculations with IU.
The Humatrope cartidges were designed for ease of use by nonmedical personelle, but if you do the math with them, they are even more confusing. They are a prefilled syringe with a cartridge in them that contains either 6 mg (18IU), 12 mg(36 IU) or 24 mg (72 IU) somatropin. The dilulent included is 3 ml of sterile water---so if you use the cartridge, it will result in either 2 mg (9 IU), 6 mg (18 IU) or 12 mg (36 IU) per ml concentration of somatropin.
Obviously this math can be very, very confusing. It gets even more confusing because different manufacturers make HGH products with different doses. For example, NovoNordisk makes Norditropin Cartridges in three concentrations: 5 mg/1.5 ml (or 3.33 mg/ml) 10 mg/1.5 ml (or 6.667 mg/ml) or 15 mg/1.5 ml (or 10 mg/ml).
My advice for anyone considering administering these sort of drugs, especially if you are doing it outside of the direct guidance of a trained medical professional, make damned sure you have something that is clearly labeled, you have the correct syringes, you double check the syringes, and you think a bit about the math involved with the dilutions.
