Understanding Insulin-Requiring Type 2 Diabetes
Type 2 diabetes is a chronic condition that develops when the body stops making enough of a hormone called insulin, or when the body’s cells don’t respond properly to the insulin that is produced. Insulin is essential because it acts like a key that opens the doors of your cells, allowing sugar (glucose) from the food you eat to enter and provide energy. Without enough working insulin, sugar builds up in the blood instead of entering cells, leading to high blood sugar levels that can damage your heart, kidneys, eyes, and nerves over time.[1]
When people with type 2 diabetes reach a point where their body can no longer produce sufficient insulin, or when other diabetes medications aren’t working well enough to control blood sugar, they need to begin insulin therapy. This doesn’t mean you now have type 1 diabetes—you still have type 2 diabetes, but your treatment has changed. Needing insulin is not a sign of failure or poor management. It’s simply the natural progression of the disease for many people.[13]
How Type 2 Diabetes Progresses
Type 2 diabetes is fundamentally different from type 1 diabetes in how it develops. In type 2, the main problem is insulin resistance, which means the body’s cells in muscles, fat, and liver don’t respond to insulin as they should. At first, the pancreas tries to compensate by making more and more insulin. However, over time, the insulin-producing cells in the pancreas—called beta cells—become worn out and start producing less insulin.[4]
Research shows that by the time someone is diagnosed with type 2 diabetes, up to half of their beta cells are already not functioning properly. The decline continues at a rate of about 4 percent each year. This progressive loss of beta-cell function is why many people with type 2 diabetes eventually need insulin therapy, even if they initially managed the condition with lifestyle changes or oral medications alone.[4]
When Insulin Therapy Becomes Necessary
Healthcare providers recommend starting insulin for people with type 2 diabetes in several situations. If you’re first diagnosed and your blood sugar level is very high—for example, 300 to 350 milligrams per deciliter or more—or if your A1C level (a measure of average blood sugar over the past few months) is greater than 9 to 12 percent, insulin may be started right away to quickly bring your blood sugar down to safer levels.[4][11]
For many people, insulin becomes necessary when their current medications—whether one or more oral drugs—are no longer keeping blood sugar within a healthy range. Guidelines suggest considering insulin when the A1C level is above 8 or 9 percent despite taking oral medications, especially if you’re experiencing symptoms of high blood sugar such as extreme thirst, frequent urination, or unexplained weight loss.[11]
Sometimes insulin is needed temporarily during specific life events. If you become pregnant, develop a severe illness, or need surgery, your body’s insulin needs may increase dramatically. In these cases, insulin might be prescribed for a short time to help manage blood sugar until the situation resolves.[13]
Types of Insulin for Type 2 Diabetes
There are several different types of insulin, and they work at different speeds and for different lengths of time. Your doctor will recommend the type that best fits your needs, and this may change over time as your condition evolves.[7]
Most people with type 2 diabetes who need insulin start with a long-acting or intermediate-acting insulin. This type of insulin is usually taken once or twice a day and works steadily throughout the day and night to keep blood sugar levels stable between meals and overnight. Common brand names include Lantus, Toujeo, Tresiba, Levemir, or Humulin I.[7][13]
If long-acting insulin alone doesn’t bring your blood sugar into the target range, you may also need a faster-acting insulin to control blood sugar spikes after meals. Rapid-acting insulin (such as NovoRapid, Humalog, or Fiasp) or short-acting insulin (such as Actrapid or Humulin S) is taken just before eating and works quickly to cover the sugar that enters your bloodstream from food.[13]
Some people use mixed insulin, also called biphasic insulin, which combines both intermediate-acting and rapid-acting insulin in one injection. This reduces the number of injections needed each day but offers less flexibility in adjusting doses. Mixed insulin is usually taken before meals, one to three times daily.[13]
How Insulin Therapy Is Started
When starting insulin for type 2 diabetes, doctors typically use one of two approaches. The first is called augmentation therapy, where insulin is added to your existing oral medications to give them extra support. This usually starts with a low dose of long-acting insulin, around 0.3 units per kilogram of body weight, taken once daily.[4]
The second approach is replacement therapy, used when your body is producing very little insulin on its own. This involves higher doses—starting around 0.6 to 1.0 units per kilogram of body weight—and often includes both long-acting (basal) insulin and rapid-acting (bolus) insulin to cover meals. About half of the total daily dose is given as basal insulin, and the other half is divided among meals.[4]
After starting insulin, your healthcare team will monitor your blood sugar levels closely and adjust your doses every three to four days until your readings are within the target range. The goal is typically to keep fasting and pre-meal blood sugar between 80 and 130 milligrams per deciliter, and blood sugar two hours after eating below 180 milligrams per deciliter.[4]
How Insulin Is Administered
Insulin must be injected because if you swallowed it as a pill, your stomach would break it down before it could work. The most common way to take insulin is with an insulin pen, which is a device that looks similar to a large pen and helps you inject safely and take the correct dose. The needles are very small and thin, and the injection goes just under the skin, not deep into muscle, so it usually doesn’t hurt.[13][6]
Other options include traditional syringes with needles, or insulin pumps, which are small devices worn on the body that deliver insulin continuously throughout the day through a tiny tube placed under the skin. There is also an inhalable form of insulin available for some people.[1]
Your diabetes nurse educator will teach you where to inject insulin—common sites include the belly, thighs, upper arms, and buttocks—and how to rotate injection sites to prevent problems with insulin absorption. Injecting repeatedly in the same spot can cause lumps under the skin called lipohypertrophy, which can interfere with how well insulin is absorbed.[4][6]
Combining Insulin with Other Medications
Even when you start insulin therapy, you usually continue taking your other diabetes medications. In fact, stopping oral medications suddenly when starting insulin can cause blood sugar to spike again. One medication in particular, called metformin, should be continued if possible because research shows it reduces the risk of death and heart problems in people with diabetes who are overweight.[4][4]
Studies have shown that taking metformin along with insulin leads to less weight gain, lower insulin doses, and fewer episodes of dangerously low blood sugar compared to using insulin alone. Other diabetes medications may also be continued or added to work alongside insulin to achieve the best blood sugar control with the fewest side effects.[4]
Potential Side Effects and Concerns
Like all treatments, insulin therapy comes with some potential side effects that are important to understand. The most serious risk is hypoglycemia, or low blood sugar, which occurs when blood sugar drops below 70 milligrams per deciliter. This can happen if there’s a mismatch between the amount of insulin you take and the carbohydrates you eat, or if you exercise more than usual or drink alcohol. Symptoms of low blood sugar include shakiness, sweating, confusion, rapid heartbeat, and feeling very hungry.[4][4]
If you think your blood sugar is low, you should check it with a glucose meter if possible, then immediately eat or drink a fast-acting carbohydrate such as juice, regular (not diet) soda, or glucose tablets. Wait 15 minutes and check your blood sugar again to make sure it has returned to normal. All people using insulin should know how to recognize and treat low blood sugar.[4]
Another common concern is weight gain. In one large study, people with type 2 diabetes who started insulin gained an average of about 4 kilograms (roughly 9 pounds). This happens because insulin promotes the storage of nutrients, may increase appetite, and can lead to “defensive eating”—eating extra food to prevent low blood sugar. The weight gain is also partly due to calories being retained in the body rather than lost in urine as sugar.[4][4]
Research comparing different insulin regimens found that certain types of insulin schedules cause more hypoglycemia or weight gain than others. Pre-mixed insulin and rapid-acting insulin before meals were associated with more episodes of low blood sugar, while insulin taken before meals was linked to more weight gain compared to long-acting insulin taken once daily.[4]
Living with Insulin Therapy
Learning to live with insulin therapy takes time and practice, but millions of people successfully manage diabetes with insulin every day. You’ll need to check your blood sugar regularly—typically before meals and sometimes after—to help you and your healthcare team adjust insulin doses appropriately. Keeping a record of your blood sugar readings and insulin doses helps identify patterns and makes it easier to fine-tune your treatment.[6]
Insulin must be stored properly to remain effective. Unopened insulin should be kept in the refrigerator but not frozen. Once you start using an insulin pen or vial, it can usually be kept at room temperature for up to a month, depending on the type. Always check the label for specific storage instructions and expiration dates.[6]
Used insulin syringes and pen needles must be disposed of safely in a sharps container—a puncture-proof container designed for medical waste—not in regular trash where they could injure someone. Many pharmacies and healthcare facilities offer sharps disposal programs.[6]
Factors that affect how quickly insulin is absorbed include where you inject it (the abdomen absorbs insulin fastest, followed by the arms, then thighs and buttocks), physical activity (exercise speeds absorption), and warm temperatures. Conversely, cold temperatures and injecting into areas with lipohypertrophy can slow insulin absorption.[4]
The Role of Insulin in Preventing Complications
The primary goal of using insulin in type 2 diabetes is to bring blood sugar levels into a safe range and keep them there. This significantly reduces the risk of serious long-term complications. Insulin helps prevent or delay damage to your eyes (diabetic retinopathy), kidneys (diabetic nephropathy), nerves (diabetic neuropathy), and blood vessels that supply your heart and brain.[2][13]
Studies have shown that better blood sugar control reduces the need for laser treatment for diabetic eye disease and lowers the risk of kidney failure and nerve damage. While intensive blood sugar control has many benefits, treatment goals should be individualized based on your age, life expectancy, other health conditions, risk of low blood sugar, and personal preferences.[11][4]
Research and Advances
Medical research continues to improve insulin therapy for people with type 2 diabetes. Newer insulin analogues—laboratory-made versions of insulin with slightly modified structures—have been shown to be just as effective as older human insulin at lowering A1C levels, but they cause less low blood sugar and fewer blood sugar spikes after meals. However, these newer insulins are significantly more expensive than older formulations.[4]
Recent studies have confirmed both the benefits and safety of insulin therapy for type 2 diabetes, though concerns about low blood sugar and weight gain remain important considerations. Research continues to focus on finding the optimal timing for starting insulin and determining which combinations of insulin with other diabetes medications work best for different individuals. Evidence shows that the benefits of insulin therapy are often offered too late, and earlier use might prevent complications.[5][5]
Scientists are also investigating the potential cancer risks associated with certain types of insulin. While one early study raised concerns about a specific long-acting insulin called glargine, diabetes organizations have concluded that any possible risk needs more research and should not limit treatment choices at this time.[4]
