When an expected insulin dose fails to lower blood sugar levels as anticipated, it results in unexpected hyperglycemia. This means the prescribed amount of insulin is not having its intended therapeutic effect, and glucose levels remain high. Troubleshooting this issue requires a systematic approach that separates problems with medication delivery from changes occurring within the body. The reasons for this failure generally fall into distinct categories: errors in the injection process, issues with the insulin product itself, or changes in the body’s physiological needs. Identifying the root cause is necessary to regain stable blood sugar control.
Issues Related to Injection Technique and Site
The most immediate cause for insulin failure is often related to how and where the medication is delivered into the body. Insulin must be injected into the subcutaneous fat layer, and improper technique can prevent the drug from being absorbed effectively. For instance, injecting too shallowly may cause the insulin to leak back out, or injecting through clothing can sometimes wipe off the dose or push bacteria into the skin.
Failure to rotate injection sites is a frequent issue, leading to the development of fatty tissue lumps called lipohypertrophy. This condition results from repeated injections into the same area, causing a buildup of fat and scar tissue. When insulin is injected into a lipohypertrophic site, absorption becomes erratic, significantly delayed, or reduced. This means the full dose does not reach the bloodstream when needed.
Air bubbles inside an insulin pen or syringe can cause under-dosing if they are not primed out before injection. Removing the needle too quickly, before the full dose is absorbed, can cause medication to leak out. Proper technique requires holding the needle in place for a few seconds after the plunger is fully depressed to ensure complete delivery. Rotating systematically between different areas—such as the abdomen, thighs, and arms—improves absorption and prevents lipohypertrophy.
Problems with the Insulin Itself
Insulin is a delicate protein highly sensitive to environmental factors, and its effectiveness can be compromised by improper storage. Insulin potency is negatively affected by exposure to extreme temperatures. While unopened insulin is typically stored in a refrigerator, freezing the product can break down the protein structure and render it inactive.
High temperatures are also damaging and cause degradation. Insulin in use should be kept out of direct sunlight and away from heat sources like car dashboards. Signs of a spoiled product include cloudiness, clumping, or discoloration in clear preparations, or a failure to properly resuspend cloudy types after gentle rolling. Using insulin past its expiration date also means the drug may have lost significant potency.
Underlying Physiological and Lifestyle Factors
Even with perfect technique and product, the body’s internal environment can increase the need for insulin. Physical stressors, such as an infection, cold, or flu, trigger the release of counter-regulatory hormones like cortisol and adrenaline. These hormones work against insulin, promoting glucose production and increasing insulin resistance, requiring a larger dose than usual.
Emotional stress, including anxiety or work pressure, also releases these stress hormones, resulting in unexplained high blood sugar levels. Insulin resistance, where the body’s cells do not respond properly to insulin, is a primary reason for needing higher doses. Resistance can worsen due to weight gain or chronic inflammation, requiring injected insulin to work harder to move glucose into the cells.
Hormonal shifts, such as those during the menstrual cycle or puberty, influence blood sugar control by temporarily increasing insulin resistance. Certain medications, including corticosteroids and some diuretics, are known to raise blood glucose. These factors necessitate a temporary or permanent increase in insulin dosage, as the standard dose becomes insufficient to overcome the body’s heightened resistance.
Immediate Action Steps and When to Seek Medical Help
If a dose of insulin appears ineffective and blood sugar remains high, the immediate priority is patient safety. First, check for ketones in the urine or blood, especially if blood sugar is above 250 mg/dL. Ketones signal that the body is breaking down fat for fuel due to a lack of effective insulin. This can rapidly lead to a medical emergency called diabetic ketoacidosis (DKA).
If ketones are present, or if you experience symptoms like nausea, vomiting, abdominal pain, or rapid, deep breathing, seek urgent medical attention immediately. If ketones are negative or only trace amounts are present, a safe correction dose of rapid-acting insulin may be needed. Wait a set amount of time, typically three to four hours from the last injection, before administering another correction dose. This waiting period prevents “insulin stacking,” where multiple doses build up and cause a severe drop in blood sugar later.
Always follow the specific correction factor and timing advice provided by a healthcare provider for re-dosing. Documenting the injection time, dose given, and blood sugar readings helps determine the cause of the problem. If high blood sugar persists despite correcting potential technique or storage issues, contact a diabetes care team to adjust the overall insulin regimen.