It was once commonly used during PCT in the belief it will aid testosterone restoration, however this is flawed due to its mechanism of action. The drug mimics the effects of LH in the body, stimulating the Leydig cells to produce testosterone in the testes . This can be fruitful in rectify existing, or avoiding testicular atrophy on cycle. It will not aid the process of recovery in the post cycle phase however, as the drug will bring about heightened oestrogen levels due to the greater aromatising of the testosterone being produced in the testes , thus bringing about greater inhibition of the HPTA .
More specifically, the methylcobalamin form of B12 is recommended, as it has been shown to be the most effective. Taking B12 gives you a huge boost of energy while training, and more importantly, greatly helps your recovery.