Wang J, Pan X, Zhou J, Li X, Sun Y, Wang L
A B12 injections effect can last anywhere from a couple of weeks to a few months, and the difference comes down to why you are deficient, how well your body holds on to B12, and the dose and schedule you are on

NAC may help by supporting antioxidant defenses and reducing oxidative stress, though its effects vary depending on the population and fertility issue being studied.32 In men, one randomized trial found that 600mg of NAC, selenium, or the combination improved semen parameters, with the combination producing stronger effects than either ingredient alone.23 In women undergoing assisted reproduction, NAC has also been studied for oocyte and embryo quality, though this research is still relatively early and not definitive.24 PCOS NAC has attracted particular interest in PCOS, where insulin resistance, inflammation, and oxidative stress often overlap.17 Researchers think NAC may help by improving insulin sensitivity and reducing oxidative stress, which may, in turn, support ovulation and reproductive function
Marianayagam, N
& Fujita, T