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 insulin can be human insulin or the insulin analogs B28Asp B28LysB29Pro or B3LysB29Glu human insulin. Most preferred 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 which render the preparation extra rapid acting and stable respectively. 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.
