How much venom does a black widow inject?

It's around 0.02 mg. Put another way, it's a very small percentage of the total volume of a spider that is not terribly large itself. It can't be extracted. read more

There’s no need to extract black widow venom. For most people, the effects of a black widow bite are very mild. See my previous answer to a similar question. read more

The venom may also kill tissue surrounding the bite. Generally, if a bite victim gets medical attention, they'll suffer minimal damage. If left untreated, a spider bite can kill, though this is very rare. In North America, the most famous dangerous spiders are the black widow and the brown recluse. read more

Female black widows, on the other hand, have quickly evolved super concentrated venom that can kill a person. Each year, about 2,200 people report being bitten by a black widow, but most recover within 24 hours with medical treatment. read more