  We consider the capture of a muon on a deuteron. An uncertainty analysis of
the dominant channels is important for a careful analysis of forthcoming
experimental data. We quantify the theoretical uncertainties of chiral
effective-field-theory predictions of the muon-deuteron capture rate from the
relevant neutron-neutron partial wave channels in the final state. We study the
dependence on the cutoff used to regularize the interactions, low-energy
constants calibrated using different fitting data and strategies, and
truncation of the effective-field-theory expansion of the currents. Combining
these approaches gives as an estimate of $\Gamma^{1/2}_{\mu d} = 399.1 \pm 7.6
\pm 4.4$ s$^{-1}$ for capture from the atomic doublet state, and
$\Gamma^{3/2}_{\mu d} = 12.31 \pm 0.47 \pm 0.04$ s$^{-1}$ for capture from the
quartet state.
