The invention relates to a soluble preparation for injection in humans, characterized in that the preparation (1) contains human insulin or a monomeric insulin analog, (2) has a lower concentration of insulin-bound zinc than about 1.8 ions per hexamer of insulin, (3) contains nicotinamide, (4) has a lower conductivity than 5 mSi/cm. The concentration of insulin-bound zinc ions is less than 0.02 ions per hexamer of insulin and the conductivity less than 0.2 mSi/cm. Further disclosed are that the preparation contains a non-ionic detergent, a preservative preferable m-cresol, an injectable preparation, said preparation being for use as a medicament for treating or preventing diabetes mellitus, use of the said preparation for the manufacture of a medicament for treating or preventing diabetes mellitus and a method of treating or preventing diabetes mellitus comprising of administering subcutaneously the said preparation to an individual in need of such treatment or prevention.
