Ligandrol (LGD-4033) is only tested in Anti-Doping (PED) tests.
This means that the only time you need to be tested for Ligandrol is if you’re playing sports on a semi-professional level or higher.
If your sporting association tests for Performance Enhancing Drugs, you should not take LGD-4033 as it will come up positive, possibly banning from the sport. If you are still going to take Ligandrol regardless of whether it is allowed or not, a safe estimate would be about 12 weeks before its not detectable (unless you are in the olympics, then it will be much greater).
Injectable steroids are injected into muscle tissue, not into the veins. They are slowly released from the muscles into the rest of the body, and may be detectable for months after last use. Injectable steroids can be oil-based or water-based. Injectable anabolic steroids which are oil-based have longer half-life than water-based steroids. Both steroid types have much longer half-lives than oral anabolic steroids. And this is proving to be a drawback for injectables as they have high probability of being detected in drug screening since their clearance times tend to be longer than orals. Athletes resolve this problem by using injectable testosterone early in the cycle then switch to orals when approaching the end of the cycle and drug testing is imminent.