Not everyone with type 2 diabetes needs to take insulin. For some people, it’s the best way to keep their blood sugar levels under control. If you are on insulin therapy, it’s important to know if your current plan is working. You don’t want to risk high blood sugar leading to long-term complications like heart disease, nerve damage, and kidney problems.

How do you know if your insulin treatment is doing a good job of managing your blood sugar levels? Being aware of a few numbers can help.

Track your blood sugar levels

Testing your blood sugar with a blood glucose meter is one of the most important ways to know if your treatment is working. If you take insulin, you’ll likely test your blood sugar two or more times a day. Your doctor will tell you how often and when to test based on the type and dose of insulin you take. Expect to go through this routine first thing in the morning before eating and potentially before and after meals, and at bedtime.

If your insulin is working, your blood sugar level will be within the range your doctor recommended. That range differs based on the time of day when you’re testing.

Here’s a general guide:

  • Before breakfast or lunch: 70–130 milligrams per deciliter (mg/dL)
  • One to two hours after meals: Less than 180 mg/dL

Each time you test, write down the results in a journal or log. Keep track of the time you tested, your insulin dose, and your blood sugar number. Bring the log with you to doctor appointments. If your numbers are outside a healthy range, you might need to talk about changing up your dosing schedule.

Know your A1Cs

Besides daily blood sugar checks, an A1C test tells you your average blood sugar levels over the last two or three months. AIC tests are given at the doctor’s office.

Like a baseball player’s batting average provides a better picture of their accomplishments over time, your A1C can say if you’re achieving good long-term blood sugar control. According to the American Diabetes Association, a good A1C goal is 7 percent for many, though it may depend on what other health conditions you have.

Watch for symptoms

Because there aren’t always symptoms with high blood sugar, looking for them alone may not be enough to know if your insulin needs some adjustment. But coupled with rising blood sugar levels, your symptoms can serve as a warning that you need to check in with your doctor.

Here are a few signs that your blood sugar is running high:

  • You feel thirstier than usual.
  • You’re unusually tired.
  • Your vision is blurred.
  • You’ve lost weight.

Signs that your blood sugar is too low include:

  • shakiness
  • sweating
  • irritability, confusion, anger, or stubbornness
  • confusion
  • fast heartbeat
  • dizziness
  • hunger
  • nausea
  • sleepiness
  • blurry vision
  • headaches
  • fatigue
  • lack of coordination
  • seizures

Look for factors that can affect blood sugar levels

Your blood sugar and A1C levels can warn you if your insulin treatment isn’t working as well as it should. Also watch out for factors that can increase your blood sugar levels and make your diabetes harder to control with insulin.

Your insulin treatment may not work as well if:

  • You’ve recently gained a lot of weight.
  • You’ve significantly changed your diet or activity level.
  • You’re taking a new medicine, such as steroids, that can increase your blood sugar levels.
  • You’ve recently had an infection.
  • Your hormones are shifting due to your menstrual cycles or a pregnancy.

You may be getting too much insulin or your kidneys may not be clearing the insulin as well if you have symptoms of hypoglycemia.

If your treatment isn’t working

If you learn that your insulin isn’t doing enough to manage your diabetes, it’s time to revisit your treatment plan.

You’ll generally visit your doctor every three to four months for checkups. These visits will give you an opportunity to go over your daily blood sugar and A1C levels, and fine-tune your treatment based on those numbers.

The first step in beating high blood sugar might be to adjust your insulin dose or timing. Often people continue some of their oral medications when starting insulin, but your doctor might also add a different oral diabetes drug to improve your blood sugar control, or may want to explore combination therapies. Your doctor can also guide you on the factors that influence blood sugar levels, such as diet, exercise, and other ways to lose weight.