How to Mix Two Insulins into the Same Syringe?

Insulin is a life-saving therapy for many people with diabetes. When you have an insulin-dependent type of diabetes, your pancreas cannot produce enough insulin or insulin at all. Without insulin injections, your blood sugar stays high, which ultimately causes severe health complications. 

Fortunately, Canadian doctors discovered insulin in 1921, literally saving the lives of thousands of diabetics. Since then, insulin therapy has become more sophisticated, and different types of insulin have been developed to allow optimal blood sugar control.

Most people with diabetes are now prescribed two or more types of insulin (generally a rapid-acting one covering meals and carbohydrate intakes and an intermediate or long-acting one covering in-between meals and overnight needs).

Some of these insulins can be mixed together in one syringe to reduce the number of daily injections. But mixing insulin isn’t that simple and should be done with caution.

So, we’re focusing here on the right way to mix two insulins into one syringe and clarifying what insulins can be mixed and what cannot.

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

Warning: If not done correctly, mixing insulin can alter the way they work and make you lose control over your blood sugar levels. Never mix two insulins unless you’ve been told to do so by your doctor or diabetes nurse. Also, make sure to only mix insulins that are compatible.

Why mixing insulin?

When you’ve been prescribed two different types of insulin, they sometimes can be mixed in the same syringe so that you need only one injection instead of two.

Mixing different types of insulin can give better blood sugar results for some patients. But before learning how to mix insulins, one should be familiar with the different types of insulins that are available, as not all of them can be mixed.

Different types of insulins

There are different types of insulin, primarily classified according to their length of action:

• Rapid-acting insulin covers insulin needs for meals eaten at the same time as the injection. It usually starts acting 10 to 15 minutes after the injection, with a peak of action after 30 to 90 minutes. Its effects last between 2 to 4 hours. Examples: Humalog (lispro insulin), Novolog (aspart insulin), and Apidra (glulisine insulin). These are clear insulins.

• Short-acting or regular insulin covers meals eaten within 20 to 60 minutes after the injection. It takes about 30 minutes to work, peaks after 2-3 hours, and lasts 3 to 6 hours after injection. Examples: Novolin R (regular insulin) or Velosulin (used for insulin pumps). These are clear insulins.

• Intermediate-acting insulin covers insulin needs for about 12 hours (half a day) or overnight. The intermediate-acting insulin used in the U.S. is NPH (N) insulin sold under the brand names Humulin-N, Novolin-N, and Novolin ReliOn. It’s often mixed with a rapid or short-acting one. It looks cloudy. 

• Long and ultra-long-acting insulins cover insulin needs for about 24 to 36 hours. They’re commonly combined with rapid or short-acting ones. Examples: Basaglar, Lantus, Toujeo (glargine insulin), Levemir (detemir insulin), and Tresiba (degludec insulin). These all are clear insulins.

Related article: A Beginner's Guide to Basal and Bolus Insulins.

Mixing insulin: pros vs. cons

Mixing insulin can be beneficial for some patients, especially those who have regular mealtimes, need to adjust insulin levels, or simply prefer taking one injection instead of two.

There may be some contraindications, though, especially for patients who find it difficult to dose insulin, don’t have regular mealtimes, have mental illnesses, or others.

In some cases, you may be prescribed pre-mixed insulin, a combination of a short-acting insulin with an intermediate or long-acting one. The ratio depends on the patient's need and may come as 75/25, 70/30, 50/50, or other. The advantage of pre-mixed insulin is that you have one injection instead of two, and you don't have to do the mixing yourself. 

Related article: Why you should use an insulin vial protector?

What insulins can be mixed?

Not all insulins can be mixed together. As a rule of thumb, intermediate-acting NPH insulin, sold under the brands Humulin-N and Novolin-N, can be mixed with rapid-acting insulin analogs and fast-acting regular insulin. 

However, glargine insulin sold under the brand names Lantus, Toujeo, and Basaglar cannot be mixed with any other insulin.

Global RPH has created a free insulin mixing tool detailing the compatibility between each insulin.

Related article: How to Read Insulin Syringes and Get the Correct Dose?

How to mix insulin the right way 

First, only mix two insulins if you have been expressively told to do so by a doctor. Then, whether you're a diabetes nurse who needs to prepare mixed insulin syringes for a diabetic patient, or a diabetic patient yourself, mixing insulin must be done the right way. Here’s how to proceed:

Related article: Can you prefill insulin syringes, and how long are they good for?

Before mixing two insulins

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

1. Check that you have the proper syringe size before starting.
2. Verify the expiration date on each insulin.
3. Wash your hand with soap and dry them properly.
4. Get the insulins and all the accessories ready on a table.

Clear before cloudy insulin

When you must mix two different types of insulin, it’s almost always a mix of a cloudy one (intermediate-acting NPH) with a clear one (rapid or short-acting).

If mixing clear and cloudy insulins in one syringe, you must always start with the clear one (the regular, short-acting insulin).

Step 1: Gently roll the vial of cloudy intermediate insulin between your palms to mix the suspension. Do not shake too hard. Next, clean the top of the bottle with an alcohol swab.

Step 2: Draw air into the syringe (an equal amount to your dose of intermediate NPH insulin) and inject it into the cloudy vial. Remove the needle without drawing any insulin yet.

Step 3: With the same syringe, draw air (an equal amount to your dose of regular insulin) and inject it into the clear insulin vial. Turn the vial upside down and draw your dose of clear insulin into the syringe.

Step 4: Draw your dose of intermediate insulin from the cloudy vial into the same syringe.

Step 5: Always make sure the total dose of clear plus cloudy insulin is correct. If you have doubts, throw away the mix into the sink and proceed again. Injecting the wrong amount of insulin can have extremely severe consequences.

Step 6: Inject your mixed insulin dose immediately.

You may sometimes be prescribed to mix two clear insulins together. In that case, it does not matter which insulin you draw first.

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

Mixing insulin: FAQs

Mixing insulin may seem complicated at first, but once you know how to do it right, it becomes a simple daily task. Here are a few frequently asked questions our team of experts answers for you. If you have any doubts, do not hesitate to reach out in the comment section below.

Related article: How long do insulin vials last, and how many do you need per month?

Can you mix nph and regular insulin?

You can mix NPH (intermediate-acting insulin, like Humulin-N and Novolin-N) and regular insulin (short-acting insulin, like Humulin-R and Novolin-R) together in the same syringe. In that case, always draw the clear one (regular) before the cloudy one (NPH).

Always do so if you’ve been told by your doctor, though.

Can Lantus be mixed with other insulins? 

No, Lantus cannot be mixed with any other insulin. Lantus is a long-acting glargine insulin with a more acidic PH than others. When injected, it forms clusters that slowly break up to create a long action. Mixing glargine insulin with other types of insulin in the same syringe changes the way it works, and you can lose control over your blood sugar.

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

Can you mix glargine and regular insulin?

As said above, glargine insulin cannot be mixed with regular insulin or any other type of insulin. Glargine insulin includes Lantus, Toujeo, and Basaglar.

Can you mix Levemir with regular insulin?

No, Levemir should never be mixed with other insulins. Levemir is a clear long-acting insulin. According to the manufacturer, Levemir may change the way in which fast-acting insulin is absorbed.

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

Can lispro be mixed with regular insulin?

Lispro insulin is sold under the brand name Humalog. It’s a clear-looking rapid-acting insulin. Technically, you can mix lispro and regular insulin, but there’s no reason you would because both are short-acting insulins. However, you can mix lispro (Humalog) with regular NPH insulin (cloudy).  

Related article: What happens if you miss a dose of insulin?

We hope this article was helpful, and we'd be happy to read your comments and experiences below.