All insulins have and need preservatives so that the insulin--whether in vials, pens, or cartridges--has some "shelf life" after the container is opened/started. Preservatives keep bacteria from growing in the containers of insulin once they've had their first use[1].

Though most of the food we eat has some kind or preservatives in it to keep it fresher longer, no one expects that a loaf of bread, will keep indefinitely in the refrigerator without becoming moldy.

The same is true for insulin; it also has preservatives in it to allow us to keep it for a given time period[2]. Just as the bread's preservatives won't keep the bread fresh forever, neither will the insulin's preservatives. This is one of the reasons manufacturers provide information regarding how long opened insulins should be kept.

Use of the wrong preservative with the various types of insulin can make it totally worthless; this is why when using manufactured diluents, care must be taken to match the proper diluent with the insulin[3].

Meta-cresol preservativeEdit

Meta-cresol Preservative

Generic Names:


Brand Names:
Non-analog Human

Humulin R, Humulin S
Actrapid, Novolin R
ReliOn/Novolin R
Insuman Rapid

Brand Names:
Non-analog Bovine

Hypurin Bovine Neutral
Insuvet Neutral, Iletin I R,

Brand Names:
Non-analog Porcine

Hypurin Porcine Neutral
Hypurin Pork Regular
Iletin II R, Pork Actrapid

Generic Names:

Aspart, Glargine
Glulisine, Lispro

Brand Names:

Novolog, NovoRapid

Brand Names:


Meta-cresol and phenol preservatives: non-mixedEdit

Meta-cresol & Phenol Preservatives: Non-mixed

Generic Names:


Brand Names:
Non-analog Human

Humulin I, Humulin N
Insulatard, Novolin N
Protaphane, Insuman Basal
ReliOn/Novolin NPH

Brand Names:
Non-analog Bovine

Hypurin Bovine Isophane
Iletin I NPH

Brand Names:
Non-analog Porcine

Hypurin Porcine Isophane
Hypurin Pork NPH
Iletin II NPH, Pork Insulatard

Generic Names:


Brand Names:


Meta-cresol and phenol preservatives: mixedEdit

Meta-cresol & Phenol Preservatives: Mixed

All intermediate-acting:

Generic Names:


Brand Names:
Non-analog Human

Actraphane 20/80, Actraphane 30/70
Actraphane 50/50
Humulin M2, Humulin M3
Humulin M5,  Humulin 70/30
Humulin 50/50, Insuman Comb 15
Insuman Comb 25, Insuman Comb 50
Mixtard 10, Mixtard 20
Mixtard 30, Mixtard 40
Mixtard 50, Novolin 70/30
ReliOn/Novolin 70/30

Brand Names:
Non-analog Porcine

Hypurin Porcine 30/70 Mix
Pork Mixtard 30

Brand Names:

Humalog 75/25, Humalog Mix 25
Humalog Mix 50Humalog 50/50
NovoMix 30, Novolog Mix

NPH/isophane,Levemir, all NPH/isophane Mixed Insulins--regardless of origin--have both m-cresol and phenol as preservatives.

Phenol preservativeEdit

Phenol Preservative

All slow-acting:

Generic Names:

Protamine Zinc Insulin[7]

Brand Names:
Non-analog Bovine/Porcine


Brand Names:
Non-analog Bovine

Hypurin Bovine Protamine Zinc
Hypurin Vet Protamine Zinc
Insuvet Protamine Zinc

PZIs contain only phenol as a preservative.

Methylparaben preservativeEdit

Methylparaben Preservative

Generic Names:

Insulin Zinc Suspension (amorphous)[8]

Brand Names:
Non-analog Porcine

Novo Semilente MC

Generic Names:
Non-analog Intermediate-acting:

Insulin Zinc Suspension[9]

Brand Names:
Non-analog Human

Humulin L, Novolin L

Brand Names:
Non-analog Bovine

Insuvet Lente
Hypurin Bovine Lente
Iletin I Lente

Brand Names:
Non-analog Porcine

Caninsulin, Vetsulin
Iletin II Lente
Monotard Pork

Generic Names:
Non-analog Slow-acting:

Insulin Zinc Suspension (crystalline)[10]

Brand Names:
Non-analog Human

Humulin U, Humulin Zn
Novolin U, Ultratard

Lente, semilente and ultralente use methylparaben as a preservative. Another name for it is methyl hydroxybenzoate[11].


  1. Diabetes Forecast-ADA, 2006-Page 5
  2. Resource Guide 2005-American Diabetes Association
  3. Lilly Discontinues Diluent for all Lente & Ultralente Insulins
  4. Insulin-InChem
  5. Insulin-InChem
  6. Insulin-InChem
  7. Insulin-InChem
  8. Insulin-InChem
  9. InChem-Insulin
  10. Insulin-InChem
  11. Insulin-InChem

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