Alpha-derivatives of cis-monounsaturated fatty acids for use as medicines. The present invention refers to pharmaceutically acceptable compounds of Formula I, their salts and derivatives, where (a) and (b) can take any value between 0 and 14, (X) can be substituted by any atom or group of atoms with an atomic/molecular weight between 4 and 200 Da and (R) can be substituted by any atom or group of atoms with an atomic/molecular weight between 1 and 200 Da, for use in the treatment of diabetes.