Serum

Any orally-administered mutagen can be concentrated into a higher-powered serum. Researchers in the Lab discovered that this gave them more bang-for-the-buck when administering the mutagen, at the cost of significantly higher demands on the subject's system. There were unconfirmed reports of significant behavioural side-effects in subjects exposed to significant amounts of particular serums, though the research in that area was regrettably halted when the Cataclysm struck.

HOWTO Serum

As with mutagens, you'll need a recipe to convert your favourite into a serum. Most sources for orally-administered can help, and there's a recipe-book specifically for each specific serums as well. The process requires Cooking skill 9-10, depending on the base product's level, and cooking the chemicals down takes a while. For the recipe-books, look in the item browser.

Once you've got your serum, you'll need a syringe to inject it. Syringes are not consumed.

In general, injecting yourself will provide you with 1-3 mutations, with an excellent chance of 2 and good odds of all 3. You'll take a Hunger, Thirst, Fatigue, and Pain hit based on the amount of mutations you gained; more mutations means a harder hit. The process is not good for your Health either, so it's good practice to eat some healthy food, like royal jelly, or shoot up a gamma globulin shot‎ afterward.

(Mutagen-writer's warning: Injecting more than two serum-shots at one time is generally a bad idea. Pace yourself!)

Why use serums?

Serums are generally more cost-effective than their associated mutagens, and can take you over the threshold. Apart from that, several folks on the forum have expressed a preference for oral mutagen, since it has fewer side effects there are various side effects, massive pain is one of the least ones, addiction is another one, and some serums might even do stranger things.