Far Cry 3
50 Achievements
1,000
25-30h
Needle Exchange
Craft 25 syringes.
15
How to unlock the Needle Exchange achievement in Far Cry 3 - Definitive Guide
Side info: Syringes have a variety of effects from healing you and pacifying/calming timid animals to letting you breathe for an extended amount of time.
You can first craft syringes in the beginning of the game after the Harvest the Jungle quest.
This is a beneficial syringe to become aquainted that will heal you using the button. It requires One green leaf.
However you cannot spam/use them if you are not injured. The easiest way to injure yourself is by using a vehicle and ramming into a tree and reversing and repeating the process as necessary SAVE FIRST. Alternatively you can repeatedly step into a small body of fire such as a lit trash can like those that are sometimes in Outposts.
Other options open up for recipes as you do more quests such as Hunters Instinct and Animal Repellent which require Amber leaves (a LOT more common) and you CAN stack/spam these ones by hitting and Navigating to Crafting>'Hunting' (under syringes).
Crafting syringes requires plants. These are scattered all over the islands, and are impossible to miss. The best and easiest ones to craft are the Medicine as they only require 1 Green plant. If you have anything else to hand that can be crafted into any other type of syringe, then you might as well use it.
Overall, this achievement will come naturally as you progress through the game. A good boosting tactic is to stock up on Green plants and find a predator animal. Let it attack you, then press and hold to heal yourself. Keep doing this and when you run out, go craft some more and then repeat the process.
Syringes can be crafted by accessing the "Craft" section in the pause menu. Plants are needed to make the final product. Plants grow everywhere in the wilderness and are displayed on the HUD when you are close to them. The most common syringes are Medicine (2 x green leaf), Animal Repellent (2 x yellow leaf) and Enhanced Perception (x2 crimson leaf). There's also a skill called "Horticulture 101" that allows you to harvest two leaves from each plant instead of just one.