Intramuscular (IM) injection needles are usually about 1 1/2 inches long. A 25 gauge (G) needle is the narrowest IM length needle that can reliably be inserted without bending.
I strongly recommend a 1 1/2 inch 25 G needle for IM menotropin injections (or for any water based medication) since the insertion is often said to be “nearly painless.” A 1 1/2 inch 22 G needle appears to be a more popular IM injection needle in certain geographic locations, but women often complain that the insertion of these larger diameter (22 G) needles is “painful.”
Many pharmacies carry 22 G needles (and not 25 G needles) as their normal stock since the 22 G is a versatile needle that can be used for virtually any (water or oil based) IM injection. However, the insertion of a 22 G needle is often said to be significantly more uncomfortable when compared to the insertion of a 25 G needle. Therefore, your pharmacy may try to convince you that a 22 G needle is just as good as a 25 G needle (since it is less work for them to sell you the 22 G needles). If you have a prescription for a 25 G needle and your pharmacy is unwilling to special order the more comfortable needles for you then you should consider using another pharmacy for your business.