How to Mix Insulin: A Step-by-Step Guide for Mixing 2 Insulins in the Same Syringe

Quick answer: To safely mix insulin, draw clear insulin into the syringe first, followed by cloudy NPH or another clear insulin. Not all types can be combined. Some long-acting insulins like Lantus and Levemir should never be mixed with others. Always double-check with your healthcare provider before mixing insulin.

If you've been prescribed more than one type of insulin, your healthcare provider may suggest mixing insulins to reduce the number of daily injections. However, knowing how to mix insulin correctly is crucial because it ensures each insulin works as intended and helps prevent dangerous blood sugar swings.

In this guide, we'll walk you through everything you need to know to mix insulin safely and effectively. You'll learn which insulins can be mixed, which insulins cannot be mixed, and the proper mixing insulin order (clear to cloudy).

We'll also break down the step-by-step process of mixing insulin NPH and regular and answer common questions.

Related article: Does Insulin Need to be Refrigerated and How to Store It Properly?

Why do some people need to mix insulin?

If you're managing diabetes with multiple daily injections, combining two types of insulin in one syringe can be a helpful and time-saving technique. Instead of taking two separate shots, mixing allows both types of insulin to be injected at once.

Some people use pre-mixed insulin, which comes ready-made from the pharmacy in fixed ratios like 70/30. But in many cases, your doctor might prescribe two separate insulins and instruct you to mix them yourself.

When mixed correctly, the insulins still work as expected: one fast or short-acting insulin covers meals and one intermediate-acting insulin keeps blood sugar steady for hours afterward.

⚠️ Important Warning: Mixing insulin incorrectly can affect how the insulin works and lead to dangerous blood sugar fluctuations. Only mix insulins if your doctor or diabetes nurse has specifically instructed you to do so. Always double-check that the types you're combining are compatible before mixing.

Related article: How Long Can You Store Prefilled Insulin Syringes?

Understanding different insulin types before mixing

Before learning how to mix insulin, it's essential to understand the different types of insulin and how they work in the body. Each type has its onset (how fast it starts working), peak (when it works the strongest), and duration (how long it lasts). Knowing this helps ensure insulin is mixed and timed correctly to control blood sugar effectively.

Rapid-Acting Insulin (Clear)

Rapid-acting insulin (also called bolus insulin or mealtime insulin) is designed to act quickly and is typically taken just before or right at the start of a meal. It begins working about 10 to 15 minutes after injection, peaks within 30 to 90 minutes, and continues to work for about 2 to 4 hours. Because of its fast action, it closely mimics how your body naturally releases insulin when you eat.

This type of insulin is ideal for controlling blood sugar spikes during or after meals. It's often used in combination with longer-acting insulins to provide around-the-clock coverage.

Examples of rapid-acting insulin include:

• Humalog (insulin lispro)
• Novolog (insulin aspart)
• Apidra (insulin glulisine)

These are clear insulins, meaning they look transparent in the vial or pen and do not need to be mixed or rolled before use.

Short-Acting or Regular Insulin (Clear)

Short-acting insulin, often called regular insulin, works more slowly than rapid-acting insulin. It's taken 20 to 60 minutes before a meal and is used to cover the rise in blood sugar from eating.

Its onset is about 30 minutes, it peaks at around 2 to 3 hours, and it can last between 3 to 6 hours. Like rapid-acting insulins, it is clear and should not appear cloudy or milky.

Examples of short-acting insulin include:

• Novolin R (regular insulin)
• Velosulin (used in insulin pumps)

Intermediate-Acting Insulin (Cloudy)

Intermediate-acting insulin is used to provide insulin coverage for about half a day or overnight. Its action isn't as fast as the previous types, but it lasts longer-usually up to 12 hours. This type of insulin is often combined with rapid or short-acting insulin to provide both immediate and extended coverage.

The most common intermediate-acting insulin used in the U.S. is NPH (Neutral Protamine Hagedorn) insulin. It comes in a cloudy suspension, meaning it must be mixed by gently rolling the vial or pen between your hands before drawing it into a syringe.

Examples of intermediate-acting insulin include:

• Humulin N
• Novolin N
• Novolin ReliOn

NPH insulin is the only cloudy insulin typically used today. The cloudiness comes from the added protein (protamine), which helps slow insulin absorption.

Long-Acting and Ultra-Long-Acting Insulin (Clear)

Long-acting and ultra-long-acting insulins (also called basal insulins) are designed to maintain a consistent insulin level in the bloodstream for 24 to 36 hours. These types are not intended to be mixed with other insulin types and should be administered as separate injections, even if they are part of the same overall insulin routine.

They are ideal for background (basal) insulin needs and are often prescribed alongside rapid-acting insulins taken at mealtimes. They help keep blood sugar levels stable throughout the day and night.

Examples of long-acting and ultra-long-acting insulins include:

• Lantus, Toujeo, and Basaglar (insulin glargine)
• Levemir (insulin detemir)
• Tresiba (insulin degludec)

These insulins are all clear, but despite their appearance, they must never be mixed in the same syringe with other insulins. Mixing them can change how they work in the body, potentially causing dangerous fluctuations in blood sugar levels.

Related article: Is Your Insulin Still Safe? What Happens When It's Left Out for 1 Hour or Overnight

Mixing insulin: Which insulins can be mixed in the same syringe?

Before we dive into the mixing steps, it's critical to know which insulins can be mixed in the same syringe. Not all insulin types are compatible; mixing the wrong kinds can result in poor blood sugar control or even dangerous side effects.

💡 If you are ever unsure about mixing insulin, Global RPH has created a free insulin mixing tool detailing the compatibility between each insulin.

Insulins that CAN be mixed:

✅ NPH insulin (intermediate-acting) can be mixed with:

• Regular insulin (short-acting)
• Lispro (rapid-acting, like Humalog)
• Aspart (rapid-acting, like Novolog)

These combinations are safe as long as you mix and inject them immediately.

Examples of safe insulin mixes:

• NPH + Regular (e.g., Humulin N + Humulin R)
• NPH + Lispro (e.g., Humulin N + Humalog)
• NPH + Aspart (e.g., Humulin N + Novolog)

What insulin CANNOT be mixed?

Several types of long-acting insulins must never be mixed with any other insulin. These insulins have unique pH levels or release mechanisms that don't work when combined with other types.

❌ Do NOT mix:

• Insulin Glargine (Lantus, Basaglar, Toujeo)
• Insulin Detemir (Levemir)
• Insulin Degludec (Tresiba)

Mixing these can affect their absorption and significantly increase the risk of hypoglycemia or other complications.

Related article: The Ultimate Guide to Traveling with Insulin: How to Keep It Refrigerated and Cool on the Go

Mixing insulin order: clear to cloudy

One of the most essential rules when combining two types of insulin in a syringe is the mixing insulin order: always draw the clear insulin first, followed by the cloudy insulin.

Why does order matter when mixing insulin?

• Drawing cloudy insulin first can contaminate the clear insulin vial with particles, potentially affecting the action of future doses.
• Drawing clear insulin first helps keep the vials sterile and ensures accurate dosing.

So if you're using NPH and regular insulin, draw up the regular insulin first, then the NPH.

Related article: Clear vs. Cloudy Insulin, Why it Matters!

Mixing insulin steps: how to mix insulin safely

Let's walk through the steps for mixing insulin so you can feel confident doing it yourself or teaching someone else.

This guide shows you how to mix insulin NPH and regular, but the process is similar when mixing NPH with Lispro or Aspart.

Related article: 10 Tips that Work to Inject Insulin Without Pain!

Before insulin mixing preparation

Before mixing insulin into a syringe, make sure to follow these prep steps carefully:

✅ Check your syringe size: Ensure you use the correct syringe for your total insulin dose. This helps avoid overfilling or underdosing.

✅ Inspect expiration dates: Double-check that both insulin vials (clear and cloudy) have not expired.

✅ Wash your hands: Use warm water and soap to clean your hands thoroughly, then dry them with a clean towel or paper towel.

✅ Set up your supplies: On a clean, flat surface like a table, gather everything you'll need:

• Your insulin vials (e.g., NPH and Regular or Rapid-Acting insulin like Lispro)
• A sterile insulin syringe
• Alcohol swabs or cotton balls with rubbing alcohol

Taking the time to prepare properly helps ensure your insulin mixture is both safe and effective.

How to mix insulin step-by-step

Now that everything is ready, here are the step-by-step instructions for mixing insulin safely and correctly:

1. Mix the cloudy Insulin: Gently roll the NPH vial between your palms 10-20 times to mix it. Don't shake it.
2. Disinfect both vial tops: Use alcohol swabs to clean the rubber stoppers of both vials.
3. Inject air into cloudy insulin (NPH): Draw air into your syringe equal to your NPH dose, then inject that air into the NPH vial. Remove the needle without drawing insulin.
4. Inject air into clear insulin (Regular or Rapid-Acting): Now, draw air equal to your clear insulin dose, inject it into the clear vial, and do not remove the needle.
5. Draw the clear insulin: Flip the vial upside down, and carefully pull back the plunger to draw the correct dose of clear insulin.
6. Draw the cloudy insulin: Now insert the needle into the NPH vial and draw your cloudy insulin dose, making sure the total units in the syringe match your prescription.
7. Inject immediately: Inject the insulin mixture right away to ensure proper action.

⚠️ If you make a mistake, discard the syringe and start again. Never try to "adjust" it by adding or removing insulin.

💡 You may sometimes be prescribed to mix two clear insulins. In that case, do these same steps, but it does not matter which insulin you draw first.

Related article: Insulin Storage: 10 Common Mistakes to Avoid When Storing Your Insulin Pens and Vials

Common Questions About Mixing Insulin

These are some of the most frequently asked questions about mixing insulin safely.

How to mix insulin NPH and regular?

• Roll the NPH vial
• Inject air into NPH (cloudy) first, then regular (clear)
• Draw up regular insulin first, then NPH
• Inject immediately

Can Lantus and Humalog be mixed?

No. Lantus (glargine) and Humalog (lispro) cannot be mixed. They must be injected separately.

Can you mix Lispro with NPH?

Yes. Lispro (rapid-acting) can be safely mixed with NPH insulin if you follow the correct mixing steps.

Which insulins can be mixed in the same syringe?

• NPH + Regular
• NPH + Lispro
• NPH + Aspart

Never mix long-acting insulins like Lantus, Basaglar, Levemir, or Tresiba.

Pre-mixed insulin vs. manual mixing

If manually mixing insulin feels overwhelming, pre-mixed insulin options may offer a simpler routine.

Standard pre-mixed formulations include:

• 70/30 (70% NPH, 30% regular)
• 75/25 (75% NPH, 25% lispro)

These are convenient but less flexible since the ratio cannot be adjusted. Manual mixing gives more control over timing and dosing.

Related article: A Step-by-Step Guide to Using Insulin Pens for Injection!

Final Tips for Mixing Insulin

Learning how to mix insulin properly can make life easier for people managing diabetes with multiple types of insulin. It reduces the number of daily injections and can improve blood sugar control, but only if done safely.

With a bit of practice, mixing insulin becomes just another part of your healthy daily routine.

Related article: TSA Rules for Diabetic Supplies: What You Need to Know Before You Travel

Key Takeaways:

Here are a few things to keep in mind:

💉 Clear Before Cloudy: Always draw clear insulin (Regular or Rapid-acting) first, then cloudy NPH-this prevents contamination and ensures accurate dosing.

🧴 Know What You Can Mix: You can mix NPH with Regular, Lispro (Humalog), or Aspart (Novolog)-but never mix Lantus, Levemir, or Toujeo with any other insulin.

🔄 Prep is Half the Work: Wash hands, gather all supplies, and check expiration dates before starting. Roll cloudy insulin gently-don't shake it.

⚠️ Mistakes Happen-Start Over: If you draw in the wrong order or see bubbles or cloudiness in the clear insulin vial, throw it out and start fresh. Don't risk incorrect dosing.

We'd Love to Hear From You!

💬 Do you have questions about mixing insulin or personal tips that make it easier? Maybe you've found the perfect routine! Share your story in the comment section below! We'd love to hear your experiences and advice.