Usually only 1 - and the times when you would need 2, the second syringe would likely be a different formulation, or brand, of filler
According to the Mayo Clinic, B12 is an essential water-soluable vitamin found in foods like fish, shellfish, meat, eggs and dairy that helps the body make DNA for new cells, form healthy red blood cells and turn food into energy
While all did an excellent job of removing the heavy metals lead, cadmium, and mercury, pitchers varied dramatically in their ability to remove chlorine, (which affects taste), fluoride, arsenic, total dissolved solids (TDS), and microplastic particles
Is GHK-Cu peptide for research available in the USA