• Although both Humulin and Humalog are insulins, Humalog is a human insulin analog which means the structure of the insulin has been modified to allow it to be absorbed more quickly than non-analog insulins.
• By switching around the sequence of two amino acids (proline at B-28 and lysine at B-29), Humalog is absorbed more rapidly and lasts for a shorter period than Humulin.
• This means Humalog insulin can be administered within 15 minutes of a meal which makes it more convenient to dose and less likely to cause hypoglycemia.
• Both Humulin and Humalog are made by Eli Lilly and company.
• Both Humulin and Humalog have the same side effects and drug interactions.

Insulin is a hormone that is produced naturally in our bodies. Its main role is to allow cells throughout the body to uptake glucose (sugar) and convert it into a form that can be used by these cells for energy. Without insulin, we cannot survive, and death from diabetes was a common occurrence until insulin was discovered in the early 1900s by Frederick Banting and Charles Best.

Humulin 70:30 and Humalog 75:25 are similar in that:

• They both contain an intermediate-acting insulin combined with a short-acting insulin
• They are both made by Eli Lilly and company
• They have the same side effects and drug interactions

They are different because:

• Humulin 70:30 contains human insulin isophane suspension as the intermediate-acting insulin and regular human insulin as its short-acting insulin
• Humalog 75:25 contains insulin lispro protamine suspension as the intermediate-acting insulin and insulin lispro as the short-acting insulin. These are both analog insulins
• One unit of Humalog insulin has the same glucose lowering effect as one unit of regular insulin but its effect is more rapid and of shorter duration
• Humalog insulin only needs to be given 15 minutes before or immediately after a meal whereas Humulin insulin need to be administered 30 minutes before a meal.

What is an insulin analog?

An insulin analog is human insulin that has been modified in a certain way to overcome some problems that occur with regular short-acting insulin. Problems such as:

• A slower onset of effect which mean regular insulin must be given 30 minutes before a meal, which may cause low blood sugar levels if a meal is delayed for any reason
• Safety concerns if a meal is not eaten within 30 minutes of administration
• A long duration of action
• A risk of post-meal low blood sugar (postprandial hypoglycemia) 4 to 6 hours after a meal
• A risk of high insulin levels.

Insulin analogs, by comparison, have a:

• A much quicker onset of action which means they can be given within 15 minutes of a meal or with food
• A shorter duration of action which lessens the risk of postprandial hypoglycemia.
• Both regular insulin and insulin analogs are man-made and their structure mimics naturally occurring human insulin. However, there are differences in the way they are made:
• Regular insulin contains hexamers of insulin crystallized around a zinc molecule. To be absorbed into the bloodstream regular insulin must first diffuse from the injection site and dissociate into dimers and monomers. Diffusion is slow, requiring 50 to 90 minutes which limits insulin absorption.
• Analog insulin is made by switching the sequence of two beta-chain amino acids. Human insulin is made up of a linked A and B polypeptide chains. In insulin lispro, for example, the proline at B-28 is switched with the lysine at B-29. This results in more rapid dissolution of the insulin to a dimer and then to a monomer which means it is absorbed more rapidly after subcutaneous injection and lasts for less than five hours.

What are the different types of Humulin?

There are several different types of Humulin and each one has been made to last for a specific length of time.

Humulin R

A short-acting insulin that:

• Starts to work within 30 minutes after injection
• Peaks in 2 to 3 hours
• Keeps working for up to 8 hours.

Humulin N

An intermediate-acting insulin that:

• Starts to work within 2 to 4 hours after injection
• Peaks in 4 to 12 hours
• Keeps working for 12 to 18 hours.

Humulin 70:30 or Humulin 50:50

A combination insulin that is usually administered 30 minutes before a meal and contains:

• A short-acting insulin
• An intermediate-acting insulin.

These pre-mixed insulins simplify dosing in people needing insulin because they already have a short-acting and an intermediate-acting insulin in them. They start to work within 10 to 20 minutes after injection, peak in 2 hours, and keep working for up to 24 hours.

What are the different types of Humalog?

There are two different types of Humalog.

Humalog (Insulin lispro)

A rapid-acting insulin that:

• Starts working within 0 to 15 minutes after administration
• Peaks in 30 to 90 minutes
• Keeps working for less than five hours (usually two to four hours).

Humalog Mix

Humalog mix combines a short-acting insulin with a longer-acting insulin. Protamine (a fish protein) is added to insulin lispro to delay its absorption and allow it to act for longer in the body. This means people do not have to inject themselves as often. Protamine insulins are cloudy and need to be remixed thoroughly before each injection.

Humalog Mix is available as:

• Humalog 50:50 which contains 50% insulin lispro protamine and 50% insulin lispro
• Humalog 75:25 which contains 75% insulin lispro protamine and 25% insulin lispro.

What are the side effects of Humulin and Humalog?

Humulin and Humalog have the same side effects because they are both insulins. Side effects of insulin include:

• Low blood sugar levels
• Weight gain, usually only when a person first starts using it
• Changes in eyesight
• Low potassium levels – may be felt as muscle pain, cramps or weakness or a funny heartbeat
• Mood changes
• A rash – usually just where you inject the insulin although some people may develop one over their whole body
• Lumps or scars where you inject the insulin.

What drugs interact with Humulin and Humalog?

Humulin and Humulog have the same interactions because they are both insulins. Interacting medicines include:

• antidepressants, such as fluoxetine or escitalopram or monoamine oxidase inhibitors such as isocarboxazid
• antipsychotics, such as aripiprazole or clozapine
• clonidine
• corticosteroids such as dexamethasone
• diuretics, such as bendroflumethiazide
• fluoroquinolones such as ciprofloxacin or levofloxacin
• HIV medicines, such as atazanavir or ritonavir
• hormones, such as estrogen, progesterone or testosterone
• lithium
• octreotide
• orlistat
• other antidiabetic agents, such as glyburide, glipizide
• pentamidine
• pentoxifylline
• propoxyphene
• pseudoephedrine
• salicylates, such as aspirin
• salmeterol
• some heart medications, such as beta-blockers (eg, atenolol or bisoprolol) ACE inhibitors (enalapril or captopril), ARBs (eg candesartan or losartan)
• sulfonamide antibiotics
• turmeric.

Note this list is not all-inclusive and does not include all medications that interact with insulin.