A two-chain insulin analogue contains Aspartic Acid at position B10 and penta-fluoro-Phenylalanine at position B24, optionally Histidine or Glutamic Acid at position A8, optionally additional substitutions or modifications at positions A13 and/or A14 and/or B28 and/or B29. The analogue may be an analogue of a mammalian insulin, such as human insulin, may optionally include (i) N-terminal deletion of one, two or three residues from the B chain, (ii) a mono-peptide or dipeptide C-terminal extension of the B-chain containing at least one acidic residue, and (iii) other modifications known in the art to enhance the stability of insulin. Formulations of the above analogues at successive strengths U-100 to U-1000 in soluble solutions at at least pH value in the range 7.0-8.0 in the absence or presence of zinc ions at a molar ratio of 0.00-0.10 zinc ions per insulin analogue monomer.