Insulin is a hormone that helps regulate blood sugar levels. It is used to treat diabetes, allowing people with the disease to manage their blood glucose. Insulin must be kept at proper temperatures to remain effective. Exposure to extreme heat or cold can cause insulin to lose its potency. Knowing what temperatures may damage insulin is essential for proper storage and use.
How Does Insulin Work?
Insulin is produced in the pancreas and released into the bloodstream. It helps glucose from food get into the body’s cells to be used for energy. Without insulin, blood sugar levels can rise dangerously high (hyperglycemia). People with diabetes either do not make enough insulin or cannot use it effectively. They must inject or inhale supplemental insulin to regulate their blood sugar.
Insulin works by binding to receptors on cell surfaces. This activates a chemical signaling pathway that allows glucose transporters to move from inside the cell to the cell wall. The glucose transporters grab glucose from the bloodstream and pull it into the cell. This lowers blood sugar levels.
Why Does Insulin Need to Be Kept Cool?
Insulin is a protein. Most proteins have a three-dimensional shape that allows them to interact with receptors and carry out functions in the body. Insulin’s structure is maintained by chemical bonds between amino acids in the protein chain. Exposure to high or low temperatures can cause insulin molecules to vibrate vigorously. This breaks the bonds holding the molecule together, permanently altering insulin’s shape and function.
Heat denatures insulin, unwinding the protein structure. Cold can cause insulin particles to crystallize. In both cases, the insulin loses its ability to lower blood sugar properly. Denatured insulin may still bind to receptors, but it will not activate them correctly, if at all. This results in elevated glucose despite taking insulin.
Storage Temperatures
Because of insulin’s vulnerability to temperature extremes, there are guidelines for proper storage:
- Unopened insulin should be stored in a refrigerator between 36°F – 46°F (2°C – 8°C).
- In-use insulin can be kept at room temperature below 86°F (30°C).
- Insulin should not be frozen.
- Insulin should not be exposed to direct heat or sunlight.
Following these recommendations keeps insulin active and effective. Let’s look at how high and low temperatures affect insulin in more detail.
Effects of High Temperatures on Insulin
Exposing insulin to high temperatures can cause it to lose potency and no longer work effectively. Here are some key points about heat and insulin:
- Temperatures above 86°F (30°C) can damage insulin. The warmer it gets, the faster insulin will get denatured.
- Direct sunlight and leaving insulin in hot vehicles is especially damaging.
- Liquid insulin is more sensitive to heat than lyophilized (freeze-dried) preparations.
- Using denatured insulin can result in hyperglycemia even when injected at the correct dose.
Why Does Heat Damage Insulin?
Insulin is made of two separate chains of amino acids folded together. This three-dimensional structure is held in place by chemical interactions between the amino acids. Heat provides energy that causes the molecules to vibrate and move more vigorously. This motion disrupts the weak bonds holding the insulin structure together.
As heat increases, the protein chains begin to unwind and separate. Imagine shaking a piece of paper back and forth. The more you shake it, the more it unfurls. This is essentially what happens to insulin at high temperatures. The protein loses its functional shape and becomes denatured.
At What Temperature Does Insulin Denature?
Insulin begins to denature at temperatures above 86°F (30°C). However, the higher the temperature rises, the faster loss of potency occurs. Some research has quantified the effects of heat on insulin degradation:
| Temperature | % Potency Lost Per Week |
|---|---|
| 98.6°F (37°C) | 5-10% |
| 104°F (40°C) | 20-40% |
| 122°F (50°C) | 25-40% |
As shown, insulin potency drops rapidly with increasing temperature exposure. Even body temperature at 98.6°F can degrade insulin over time. Exposing insulin to temps above 104°F can destroy 20-40% of its effectiveness in just one week.
Precautions Against Heat Damage
Some tips to avoid heat damaging insulin include:
- Store unopened insulin in the refrigerator, not the freezer.
- Don’t leave insulin vials in hot vehicles or direct sunlight.
- Keep insulin pens or pumps from getting too warm by not wearing directly against skin.
- Discard any insulin that has been exposed to temperatures above 86°F (30°C).
Being careful to control insulin’s exposure to heat will help keep it active and usable for controlling blood glucose.
Effects of Freezing on Insulin
Freezing insulin can also affect its potency and function. Here are some key points on insulin and cold temperatures:
- Insulin should never be frozen. Temperatures below 32°F (0°C) damage insulin.
- The tubes in insulin pumps can freeze, blocking insulin delivery.
- Ice crystals that form during freezing can irreversibly change insulin’s structure.
- Using previously frozen insulin may result in hyperglycemia.
Why Does Freezing Damage Insulin?
When water in insulin solutions freezes, it forms ice crystals. Insulin molecules are forced together around these crystals in concentrated clumps. This disrupts the normal interactions between the protein chains that maintain insulin’s shape.
In addition, the formation of ice crystals causes physical stress on the insulin particles. Even slight shaking or vibration can permanently alter insulin’s structure. The vigorous molecular motion during freezing seriously damages insulin molecules.
At What Temperature Does Insulin Freeze?
Insulin begins to freeze around 32°F (0°C). However, damage may occur at slightly warmer temperatures as well. For example, refrigerators often cool to near freezing temperatures. Storing insulin in the back of the refrigerator or close to the cooling element puts it at higher risk of accidental freezing.
Research has looked at the effects of freezing on insulin potency:
| Temperature | % Potency Lost |
|---|---|
| 5°F (-15°C) | 25-40% after 2 weeks |
| -4°F (-20°C) | 40-60% after 2 weeks |
Allowing insulin to freeze, even at typical refrigerator freezing temperatures near 32°F can significantly degrade insulin. Storing at below 0°F temperatures can destroy 25-60% of insulin activity in just two weeks.
Avoiding Freeze Damage
Tips to prevent insulin being damaged by accidental freezing:
- Do not store insulin in the refrigerator door where freezing is most likely.
- Avoid the back of the refrigerator near the cooling element.
- Check that refrigerator is maintaining 2°C – 8°C temperature.
- Never freeze insulin vials or pens even if thawing later.
- Take precautions against infusion set tubes freezing in insulin pumps.
Being aware of conditions that could freeze insulin allows steps to be taken to keep it at safe temperatures.
Signs of Heat or Freeze Damaged Insulin
Denatured, ineffective insulin may not be obvious. Here are some signs that insulin may have been damaged:
- Clumping – Insulin has obvious clumps or frost-like particles.
- Cloudiness – Insulin solution appears hazy.
- Discoloration – Insulin has changed from clear to yellow/brown.
- Solid crystals – Jagged ice crystals visible in the insulin.
- Foam – Bubbles or foam present after swirling insulin.
Even if insulin does not show visible signs, damage may have still occurred. Erratic blood sugar levels, hyperglycemia, and less stable glucose control could indicate insulin is not working properly. When in doubt, replace insulin that could have been exposed to temperature extremes.
Can Damaged Insulin Be Used?
Insulin that may have been exposed to heat over 86°F or freezing temperatures below 32°F should not be used. The risks include:
- Erratic blood glucose – Denatured insulin may not lower glucose properly.
- Hyperglycemia – Ineffective insulin results in high blood sugar.
- DKA risk – Loss of glucose control raises risk of diabetic ketoacidosis.
- Adverse effects – Denatured insulin may provoke immune reactions.
While damaged insulin may still bind receptors, it will not have the proper effect of lowering blood sugar. Using denatured insulin puts diabetic patients at risk of hyperglycemia and DKA. Only insulin confirmed to have been stored at appropriate temperatures should be used.
Can Damaged Insulin Be Reused if Thawed?
Insulin that has frozen should never be used after thawing. The damage done by ice crystals is permanent. Thawing does not “reactivate” the insulin. All frozen insulin should be safely discarded.
Proper Insulin Temperature Storage
To avoid damage, insulin must be stored properly. Recommendations include:
- Refrigeration – Unopened insulin should be stored in a refrigerator between 36°F – 46°F (2°C – 8°C).
- Room temperature – In-use insulin can be kept unrefrigerated at up to 86°F (30°C).
- Avoid heat – Do not expose insulin to direct sun or leave in hot vehicles.
- Avoid freezing – Do not allow insulin to freeze. Avoid the refrigerator door or cooling element.
- Travel cases – Use insulated cases when traveling with insulin.
Following storage guidelines keeps insulin stable and effective for managing blood glucose levels.
Discarding Bad Insulin
Insulin that has been exposed to extreme heat or freezing should be safely discarded. Here are some tips for disposing of bad insulin:
- Do not simply throw vials or pens in the trash. Needle sticks can harm others.
- Remove the needle and replace the cap on pens or syringes before disposal.
- Mix insulin with an undesirable substance like coffee grounds or kitty litter.
- Place insulin in an empty detergent bottle or other opaque container before throwing away.
- Some municipalities have special waste procedures for medical sharps disposal.
Properly disposing of unused insulin protects others from potential needle stick injuries. Damaged insulin should always be safely discarded and replaced.
Getting Replacements for Damaged Insulin
If your insulin supply has been exposed to heat or freezing and needs to be replaced, speak with your doctor or pharmacy. Options may include:
- Contacting your health insurance provider to request replacement vials or pens.
- Filling a prescription refill from your doctor for more insulin.
- Getting samples of insulin from your endocrinologist or diabetes educator.
- If uninsured, contacting prescription assistance programs or the insulin manufacturer.
Throwing out damaged insulin should prompt immediately making arrangements to obtain fresh, usable insulin. This ensures you maintain an adequate insulin supply.
Key Points
- Temperatures above 86°F (30°C) can denature insulin, rendering it ineffective.
- Freezing insulin causes permanent damage from ice crystals forming.
- Storing insulin properly in the refrigerator or at room temperature prevents damage.
- Signs of damaged insulin include clumping, cloudiness, or discoloration.
- Using heat or freeze damaged insulin puts diabetics at risk of hyperglycemia.
- Insulin damaged by temperature extremes should be safely discarded and replaced immediately.
The Bottom Line
Insulin is highly sensitive to temperatures outside its recommended storage range. Exposing insulin to excess heat over 86°F denatures the protein so it cannot properly lower blood sugar. Freezing insulin causes irreversible damage from ice crystals distorting its molecular structure. Using damaged insulin can result in loss of glucose control for diabetics.
Always store insulin properly, whether refrigerated or at room temperature. Inspect vials and pens for any signs of heat or freeze related damage. If in doubt, replace the insulin. With proper storage and vigilance, insulin can be kept in ideal condition for managing diabetes.
