Type 2 Diabetes and Insulin: What You Need to Know

18 Sep 2025 By Michael S. Underhill, D.O.

Type 2 Diabetes and Insulin: What You Need to Know

Type 2 diabetes is a chronic condition that affects the way your body metabolizes sugar (glucose), an important source of energy. With type 2 diabetes, your body either resists the effects of insulin — a hormone that regulates the movement of sugar into your cells — or doesn't produce enough insulin to maintain normal glucose levels. Insulin resistance and relative insulin deficiency are hallmarks of this condition.

This can lead to a buildup of sugar in the bloodstream, which can eventually cause serious health problems, such as heart disease, vision loss, and kidney disease. Managing type 2 diabetes often involves lifestyle changes, such as diet and exercise. However, for many people, these changes alone aren't enough, and medication becomes necessary. Insulin therapy is a key treatment option for type 2 diabetes, especially when other treatments aren't sufficient to control blood sugar levels.

Key Takeaways About Type 2 Diabetes and Insulin:

Insulin resistance and insufficient insulin production are core issues in type 2 diabetes.
Lifestyle changes are often the first step in managing the condition, but medication, including insulin, is frequently required.
Insulin therapy helps lower blood sugar levels by facilitating glucose uptake into cells.
Various types of insulin are available, each with different onset and duration of action, allowing for customized treatment plans.
Proper insulin administration technique and blood sugar monitoring are essential for safe and effective insulin therapy.

How Insulin Works in Type 2 Diabetes

To understand the role of insulin in type 2 diabetes, it's important to first grasp how insulin functions in a healthy body.

Normal Insulin Function: When you eat, your pancreas releases insulin, which acts like a key to allow sugar (glucose) from the food you eat to enter cells in your body for energy.
Type 2 Diabetes Complications: In type 2 diabetes, either your body doesn't make enough insulin, or your cells become resistant to insulin's effects (insulin resistance). This leads to glucose accumulating in your bloodstream, causing high blood sugar levels.
The Need for Insulin Therapy: When lifestyle modifications and other medications fail to adequately control blood sugar levels, insulin therapy becomes necessary. It helps lower blood sugar levels by supplementing the body's own insulin production or overcoming insulin resistance.

The Role of Insulin in Managing Blood Sugar

Insulin therapy effectively bridges the gap by either supplementing the body's own insulin or helping overcome insulin resistance. Here’s a more detailed explanation:

Supplementing Insulin Production: For individuals whose pancreas does not produce enough insulin, insulin injections provide the necessary hormone to facilitate glucose uptake into cells.
Overcoming Insulin Resistance: In some cases, even when the pancreas produces insulin, the body's cells do not respond efficiently. Insulin therapy, especially at higher doses, can help push glucose into these resistant cells.

The table below summarizes the key differences in how insulin functions in healthy individuals versus those with type 2 diabetes:

| Feature | Healthy Individuals | Type 2 Diabetes | | -------------------- | ------------------------------- | ------------------------------- | | Insulin Production | Normal | Insufficient or impaired | | Insulin Sensitivity | Normal | Insulin resistance present | | Glucose Regulation | Effective | Ineffective, leading to hyperglycemia | | Need for Insulin Therapy | Not required | Often required |

Types of Insulin Used in Type 2 Diabetes

There are several types of insulin available, each with a different onset (how quickly it starts working) and duration (how long it lasts). Your doctor will prescribe the most appropriate type or combination of types based on your individual needs, lifestyle, and blood sugar patterns. Here's an overview of common insulin types:

Rapid-Acting Insulin: Starts working within 15 minutes, peaks in about 1 hour, and lasts for 2-4 hours. This type is often taken before meals to cover the glucose from the food you're about to eat.
- Examples: Insulin lispro (Humalog), insulin aspart (NovoLog), insulin glulisine (Apidra)
- Short-Acting Insulin (Regular Insulin): Starts working within 30 minutes to 1 hour, peaks in 2-3 hours, and lasts for 3-6 hours. Also taken before meals, but needs to be administered further in advance.
- Example: Human regular insulin (Humulin R, Novolin R)
- Intermediate-Acting Insulin: Starts working in 2-4 hours, peaks in 4-12 hours, and lasts for 12-18 hours. This provides a base level of insulin coverage.
- Example: NPH insulin (Humulin N, Novolin N)
- Long-Acting Insulin: Starts working several hours after injection and lasts for 24 hours or longer. Provides a constant, steady level of insulin.
- Examples: Insulin glargine (Lantus, Basaglar), insulin detemir (Levemir), insulin degludec (Tresiba) Unlock Steady Energy 10 Simple Habits For Blood Sugar Balance
- Ultra-Long Acting Insulin: Starts working in about 6 hours and lasts for 36 hours or longer. It provides a very stable and prolonged basal insulin level.
- Example: Insulin degludec (Tresiba - depending on dosage)
- Premixed Insulin: These contain a combination of two types of insulin, usually a rapid- or short-acting insulin and an intermediate-acting insulin. They offer convenience by reducing the number of injections required.
- Examples: Humulin 70/30 (70% NPH insulin and 30% regular insulin), NovoLog Mix 70/30 (70% insulin aspart protamine and 30% insulin aspart)

The following table provides a comparative summary:

| Insulin Type | Onset (hours) | Peak (hours) | Duration (hours) | Usage | | ------------------------ | ------------- | ------------ | ---------------- | ------------------------------------------ | | Rapid-Acting | 0.25 | 1 | 2-4 | Before meals | | Short-Acting (Regular) | 0.5-1 | 2-3 | 3-6 | Before meals | | Intermediate-Acting (NPH) | 2-4 | 4-12 | 12-18 | Basal insulin | | Long-Acting | 1-4 | None | 20-24 | Basal insulin | | Ultra-Long Acting | 6 | Minimal | 36+ | Basal insulin | | Premixed | Varies | Varies | Up to 24 | Meal and basal coverage |

Note: Onset, peak, and duration can vary depending on the individual, dosage, and injection site.

Choosing the Right Insulin

The selection of insulin types and dosage is a highly individualized process. Factors influencing the choice include: The Top 8 Factors Affecting Your Blood Sugar Levels Besides Food

Blood Sugar Levels: Monitoring and assessing patterns of high and low blood sugar is crucial.
Lifestyle: Eating habits, physical activity, and daily routines play significant roles.
Overall Health: Other medical conditions can influence insulin requirements.
Individual Response: How each person responds to a specific insulin.

Administering Insulin: Techniques and Best Practices

Proper insulin administration is essential for its effectiveness and to minimize complications. Here’s a step-by-step guide and best practices:

Wash Your Hands: Always start by washing your hands thoroughly with soap and water.
Inspect the Insulin: Check the insulin vial or pen for any abnormalities, such as clumping, frosting, or changes in color. If you notice any of these, do not use it.
Prepare the Injection Site: Choose an injection site on your abdomen (at least two inches away from your navel), thigh, upper arm, or buttocks. Rotate injection sites to prevent lipohypertrophy (lumps under the skin). Clean the injection site with an alcohol swab and allow it to dry.
Prime the Pen/Prepare the Syringe: If using an insulin pen, prime it according to the manufacturer's instructions. This typically involves dialing up two units of insulin and injecting it into the air to remove any air bubbles. If using a syringe, draw the correct dose of insulin into the syringe, being careful to avoid air bubbles.
Inject the Insulin: Pinch the skin at the injection site to create a fold. Insert the needle at a 90-degree angle (or a 45-degree angle if you're very thin). Push the plunger all the way in to deliver the full dose of insulin.
Hold and Count: After injecting the insulin, hold the needle in place for 5-10 seconds to ensure the entire dose is delivered.
Remove the Needle and Dispose: Carefully remove the needle and dispose of it in a sharps container. Do not reuse needles.

Best Practices for Insulin Administration

Rotate Injection Sites: To prevent lipohypertrophy, rotate injection sites systematically. Keep a log of where you inject each time.
Consistent Timing: Inject insulin at the same time each day to maintain consistent blood sugar control.
Proper Storage: Store insulin properly, typically in the refrigerator (but do not freeze). Follow the manufacturer's instructions for storage after opening.
Needle Length: Use the appropriate needle length to ensure insulin is delivered into the subcutaneous tissue (the layer of fat under the skin), not into muscle. Shorter needles may be preferable for thinner individuals.

Avoiding Common Mistakes

Not Rotating Injection Sites: This can lead to lipohypertrophy, affecting insulin absorption.
Reusing Needles: Reusing needles can increase the risk of infection and reduce insulin effectiveness.
Injecting into Muscle: This can cause rapid insulin absorption and hypoglycemia.
Improper Storage: Storing insulin at incorrect temperatures can degrade its effectiveness.

Additional Tips

Educate Yourself: Attend diabetes education classes to learn more about insulin administration and management.
Consult Your Healthcare Provider: Regularly discuss your insulin regimen and any challenges you're experiencing with your healthcare provider.
Emergency Preparedness: Carry a medical ID and inform friends, family, and coworkers about your diabetes and insulin use.

Monitoring Blood Sugar While on Insulin

Regular blood sugar monitoring is an essential part of managing type 2 diabetes, especially when you're taking insulin. Monitoring helps you understand how your body is responding to insulin, diet, and exercise, and allows you to make adjustments as needed to keep your blood sugar levels within your target range. A Practical Guide To Reading A Blood Sugar Chart For Persons With Diabetes

Why is Blood Sugar Monitoring Important?

Personalized Management: Monitoring allows you to tailor your insulin doses and meal plans based on your individual responses.
Preventing Complications: Keeping blood sugar levels in a healthy range reduces the risk of long-term complications such as heart disease, kidney disease, and nerve damage.
Avoiding Hypoglycemia: Monitoring helps you identify and treat low blood sugar (hypoglycemia) promptly, which can be a dangerous side effect of insulin therapy.
Avoiding Hyperglycemia: Monitoring helps you identify and address high blood sugar (hyperglycemia) promptly, reducing potential short-term and long-term risks.

How to Monitor Blood Sugar

Using a Blood Glucose Meter:
- Test Strips: Ensure the test strips are not expired and are compatible with your meter.
- Lancing Device: Use a lancing device to prick your finger and obtain a small drop of blood.
- Applying Blood: Apply the blood to the test strip as directed by the meter's instructions.
- Reading the Result: Wait for the meter to display your blood sugar level.
Continuous Glucose Monitoring (CGM):
- Sensor Insertion: A small sensor is inserted under the skin, usually on the abdomen or arm.
- Real-Time Readings: The sensor continuously measures glucose levels in the interstitial fluid and transmits the data to a receiver or smartphone app.
- Trends and Alerts: CGMs provide real-time glucose readings, trend arrows indicating the direction and speed of glucose changes, and alerts for high and low glucose levels.

Frequency of Monitoring

The frequency of blood sugar monitoring depends on several factors, including the type of insulin you're taking, your blood sugar control, and your doctor's recommendations. Here are some general guidelines:

Multiple Daily Injections (MDI): If you're taking multiple daily injections of insulin, you may need to check your blood sugar several times a day, such as before meals, before bedtime, and occasionally after meals.
Insulin Pump Therapy: If you're using an insulin pump, you may need to check your blood sugar less frequently, but still regularly, especially before meals and bedtime.
Less Frequent Monitoring: If you’re using long-acting insulin, or oral medications, your doctor may advise less frequent monitoring.

| Insulin Regimen | Recommended Monitoring Frequency | | ---------------------------------------- | --------------------------------------------------------------------- | | Multiple Daily Injections (MDI) | Several times a day (before meals, before bedtime, occasionally after meals) | | Insulin Pump Therapy | Regularly, especially before meals and bedtime | | Long-Acting Insulin or Oral Medications | Less frequent, as advised by your healthcare provider |

Target Blood Sugar Ranges

Your healthcare provider will help you establish target blood sugar ranges that are right for you. General guidelines are:

Before Meals: 80-130 mg/dL
Two Hours After Meals: Less than 180 mg/dL
HbA1c: Less than 7% (a measure of average blood sugar over the past 2-3 months)

Using Monitoring Data to Adjust Insulin

It’s important to understand how to use your blood sugar data to make informed adjustments to your insulin dosage. Keeping a logbook or using a digital app to track your blood sugar levels, insulin doses, diet, and exercise can provide valuable insights. Look for patterns and discuss them with your healthcare provider.

Adjusting Insulin:

High Blood Sugar: If blood sugar is consistently high before a particular meal, your doctor might suggest increasing the pre-meal insulin dose.
Low Blood Sugar: If blood sugar is frequently low, your doctor might suggest reducing the insulin dose, or adjusting your carbohydrate intake.

Additional Tips for Effective Monitoring

Consistency: Use the same meter and test strips to ensure consistent results.
Record Keeping: Keep a detailed log of your blood sugar readings, insulin doses, and any other relevant information.
Communication: Regularly discuss your monitoring results with your healthcare provider to make informed decisions about your diabetes management plan.

Potential Side Effects of Insulin Therapy

While insulin is a life-saving medication for many people with type 2 diabetes, it can have potential side effects. Being aware of these side effects and knowing how to manage them is important for safe and effective insulin therapy.

Common Side Effects

Hypoglycemia (Low Blood Sugar): This is the most common side effect of insulin therapy. It occurs when blood sugar levels drop too low (typically below 70 mg/dL).
- Symptoms: Shakiness, sweating, dizziness, confusion, irritability, rapid heartbeat, hunger.
- Management: Carry a source of fast-acting glucose (such as glucose tablets, juice, or regular soda) to treat hypoglycemia. Follow the "15-15 rule": consume 15 grams of fast-acting glucose, wait 15 minutes, check your blood sugar, and repeat if necessary.
- Weight Gain: Insulin can promote weight gain because it helps glucose enter cells, where it can be stored as energy. Additionally, when blood sugar levels are better controlled, calories that were previously being excreted in the urine are now retained, contributing to weight gain.
- Management: Work with a registered dietitian to develop a healthy eating plan that helps manage your weight. Regular physical activity is also important.
- Lipohypertrophy: This is the buildup of fatty tissue under the skin at the injection site. It can occur if you repeatedly inject insulin in the same area.
- Management: Rotate injection sites systematically to prevent lipohypertrophy. Avoid injecting into areas where lipohypertrophy has already occurred.
- Injection Site Reactions: These can include redness, swelling, itching, or pain at the injection site.
- Management: Ensure you are using proper injection technique and cleaning the injection site with an alcohol swab before injecting. Rotate injection sites to reduce irritation.
- Edema (Swelling): Insulin can sometimes cause fluid retention, leading to swelling in the feet, ankles, or hands.
- Management: This is usually temporary and resolves on its own. However, if it persists or becomes severe, consult your healthcare provider.

Rare but Serious Side Effects

Severe Allergic Reaction (Anaphylaxis): Although rare, some people may experience a severe allergic reaction to insulin, which can be life-threatening.
- Symptoms: Hives, difficulty breathing, swelling of the face, lips, or tongue, rapid heartbeat, dizziness, loss of consciousness.
- Management: Seek immediate medical attention.
- Hypokalemia (Low Potassium): Insulin can cause potassium to move from the bloodstream into cells, which can lead to low potassium levels in the blood.
- Symptoms: Muscle weakness, fatigue, heart palpitations, constipation.
- Management: Your healthcare provider may monitor your potassium levels and recommend potassium supplements if needed.

Strategies for Managing Side Effects

Regular Monitoring: Monitor your blood sugar levels regularly to prevent hypoglycemia and hyperglycemia.
Education: Learn about the potential side effects of insulin therapy and how to manage them.
Communication with Healthcare Provider: Discuss any concerns or side effects you're experiencing with your healthcare provider. They can adjust your insulin dosage or recommend other treatments to help manage side effects.
Healthy Lifestyle: Maintain a healthy lifestyle, including a balanced diet and regular physical activity, to help manage your weight and improve your overall health.

Tips for Preventing Hypoglycemia

Consistent Meal Timing: Eat meals and snacks at regular intervals.
Carbohydrate Balance: Balance your carbohydrate intake with your insulin dose.
Exercise Awareness: Be aware of how exercise affects your blood sugar levels and adjust your insulin dose or carbohydrate intake accordingly.
Alcohol Consumption: Be cautious about alcohol consumption, as it can increase the risk of hypoglycemia.
Medical ID: Wear a medical ID bracelet or necklace indicating that you have diabetes and take insulin.