Insulin is a hormone that helps your body process blood glucose (blood sugar). Some people with type 2 diabetes inject insulin to help keep their blood sugar levels in a healthy range.

Over time, insulin can become less effective. There are a few possible reasons for this. If your blood sugar levels start to rise even though you’re taking your insulin as prescribed, talk to your doctor. They can help you figure out what’s going on. You may need to adjust how you take insulin or try a different treatment plan for diabetes.

Here are some common issues that can make insulin less effective.

Why Isn’t Your Insulin Working Anymore?

Understanding why insulin might stop working can help you find a solution. Any of these situations could be the cause:

• You’re not injecting it correctly.
• Your medication has gone bad.
• You missed a dose (or two).
• You’re stressed or sick.
• You’ve developed more insulin resistance.

It’s normal for your body’s response to insulin to change over time. Sometimes it’s due to one cause — sometimes several. The following steps can help you address the most likely issues.

1. Check Your Injection Technique

Insulin needs to be injected into the layer of fat under the skin (called subcutaneous fat). If you inject it too shallowly or too deep, it may not work properly. Make sure to use the right size needles and the proper injection angle — usually 90 degrees or 45 degrees.

It’s also important to rotate your injection sites. Injecting in the same place too often can cause complications that affect how your body absorbs insulin. Good injection areas include the abdomen, thighs, buttocks, and upper arms.

Even people who have used insulin therapy for years can make mistakes. It’s a good idea to ask your doctor or diabetes educator to check your supplies and technique. They can make sure you’re using the right equipment, measuring doses correctly, and injecting in a safe, effective way.

2. Store and Handle Insulin Properly

Insulin won’t work as well if it’s not in good condition. Always follow the instructions that come with your medication. In general, insulin should be stored in the refrigerator. That way, it will stay good until it expires. If a refrigerator isn’t available, you can store it in a cool and dark space, but only for about four weeks.

Never freeze insulin or expose it to direct sunlight. Extreme temperatures — either hot or cold — can damage it. If you think your insulin has been exposed to unsafe conditions, contact your healthcare provider or pharmacist before using it.

If you use insulin pens, remove the needle after each injection. Storing the pen with the needle attached can cause clogs and leaks that make your doses less accurate.

3. Track Your Blood Sugar Patterns

Blood sugar levels naturally rise and fall throughout the day. While finger-prick testing gives valuable snapshots, it’s not always realistic to check before and after every meal. A continuous glucose monitor can help by tracking your blood sugar around the clock. This gives you and your healthcare team detailed information about highs, lows, and patterns you might not notice otherwise.

If your insulin doesn’t seem to be working, monitoring your blood sugar closely is one of the best ways to identify what’s going on and adjust your plan safely.

4. Take a Closer Look at Your Lifestyle Habits

Lifestyle plays a major role in blood sugar management. If your blood sugar stays high even when you’re taking insulin as prescribed, other factors might be contributing — or your body may be developing greater insulin resistance.

Possible reasons for high blood sugar (despite insulin therapy) include:

• Eating too many carbohydrates at once
• Not getting enough physical activity
• Psychological stress
• Lack of sleep
• Taking other medications (like steroids)

Insulin resistance happens when your body doesn’t respond to insulin as well as it used to. This causes high blood sugar. Weight gain and certain hormonal conditions can make insulin resistance more likely. In some cases, certain lifestyle changes can help reverse it. Other times, you may need a higher dose of insulin or another treatment to lower blood sugar.

5. Ask About Adjusting Your Treatment Plan

Type 2 diabetes is a long-term condition, and managing blood sugar is an ongoing process. If your current insulin isn’t working well, your endocrinologist may recommend changing your type, timing, or delivery method.

There are several kinds of insulin. Some work quickly (short-acting), while others last much longer (long-acting). Insulin pumps are another option that helps take some of the guesswork out of injecting insulin. Talk with your healthcare provider about whether trying a new approach might help.

If you are prescribed different types of insulin, it’s important to understand how long each one lasts and when to take it in relation to your meals and daily schedule.

People with type 2 diabetes may also take other medications with or instead of insulin to lower blood sugar. Common examples include:

• Metformin
• Dipeptidyl peptidase 4 (DPP-4) inhibitors
• Medications that target glucagon-like peptide 1 (GLP-1)
• Sodium-glucose cotransporter 2 (SGLT2) inhibitors
• Sulfonylureas
• Thiazolidinediones (TZDs)

Medication is only one part of diabetes care. Combining your treatment with healthy lifestyle habits is key to protecting your long-term health. If you need help planning a diabetes-friendly diet, ask for a referral to a registered dietitian. Regular physical activity, getting enough sleep, and managing stress can also help support weight loss and reverse insulin resistance to an extent.

If you’re struggling emotionally, a mental health counselor can help you find healthy ways to cope without letting stress or frustration affect your diabetes management.

Stay Positive and Seek Solutions

It’s normal to feel frustrated when your blood sugar rises despite your best efforts. You may have been in a good groove with insulin therapy, only to have a setback at your next blood test.

But diabetes management often requires ongoing adjustments — and setbacks don’t mean failure. The most important thing is to stay informed and aware. High blood sugar levels are treatable. Knowing where your blood sugar stands will help you take action and avoid serious complications.

Fortunately, you don’t have to figure everything out on your own. Your healthcare team has experience helping people manage diabetes successfully. Reaching out to a diabetes community — online or in person — can also help you feel supported and less alone.

Join the Conversation

On DiabetesTeam, people share their experiences with type 2 diabetes, get advice, and find support from others who understand.

Have you struggled to control type 2 diabetes with insulin? Let others know in the comments below.