Two-pion contribution to the absorptive part of nucleon-nucleon scattering amplitudes in the unphysical region is calculated using the dispersion for pion-nucleon scattering. The dispersion relations with this absorptive part are used for analyzing nucleon-nucleon scattering data at low energy and at moderate energy, and we find good agreement if we choose the coupling constant as f2 / 4π= 0.08 ±0.01.