  We present a spectroscopic analysis of a sample of 48 M dwarf stars ($0.2
M_{\odot}< M < 0.6 M_{\odot}$) from the Hyades open cluster using
high-resolution H-band spectra from the SDSS/APOGEE survey. Our methodology
adopts spectrum synthesis with LTE MARCS model atmospheres, along with the
APOGEE DR17 line list, to determine effective temperatures, surface gravities,
metallicities, and projected rotational velocities. The median metallicity
obtained for the Hyades M dwarfs is [M/H]= 0.09$\pm$0.03 dex, indicating a
small internal uncertainty and good agreement with optical results for Hyades
red-giants. Overall, the median radii are larger than predicted by stellar
models by 1.6$\pm$2.3\% and 2.4$\pm$2.3\%, relative to a MIST and DARTMOUTH
isochrone, respectively. We emphasize, however, that these isochrones are
different and the fractional radius inflation for the fully- and
partially-convective regimes have distinct behaviors depending on the
isochrone. Using a MIST isochrone there is no evidence of radius inflation for
the fully convective stars, while for the partially convective M-dwarfs the
radii are inflated by 2.7$\pm$2.1\%, which is in agreement with predictions
from models that include magnetic fields. For the partially-convective stars,
rapid-rotators present on average higher inflation levels than slow-rotators.
The comparison with SPOTS isochrone models indicates that the derived M dwarf
radii can be explained by accounting for stellar spots in the photosphere of
the stars, with 76\% of the studied M dwarfs having up to 20\% spot coverage,
and the most inflated stars with $\sim$20 -- 40\% spot coverage.
