Long-acting insulin, often referred to as basal insulin, is designed to provide a steady, low level of insulin throughout the day and night. This consistent delivery mimics the normal, background insulin secretion of a non-diabetic pancreas. Its primary purpose is to regulate the glucose that the liver continuously releases into the bloodstream, even when a person is not eating. Because it works to maintain a stable baseline for up to 24 hours or longer, consistent daily dosing is considered the standard practice for safety and effective glucose management. The decision to modify or hold this medication is a serious one that should always be approached with caution.
The Fundamental Rule: Why Basal Insulin Must Not Be Stopped
The default position in diabetes management is that you should continue to take your long-acting insulin every day, regardless of your food intake. The body requires a constant supply of insulin because the liver naturally produces and releases glucose into the bloodstream around the clock. This process, called gluconeogenesis, occurs even during periods of fasting or sleep to fuel the brain and other organs. Without basal insulin to counteract this hepatic glucose output, blood sugar levels will inevitably rise.
Stopping the long-acting dose leads directly to a state of profound insulin deficiency. When the body lacks insulin, it cannot use glucose for energy and begins to break down fat for fuel instead. This process generates acidic byproducts known as ketones, which accumulate in the blood. If this state persists, it can rapidly lead to Diabetic Ketoacidosis (DKA), a dangerous medical emergency requiring immediate hospital treatment. For this reason, the long-acting insulin dose should never be completely omitted without explicit instruction from a healthcare provider.
Adjusting Dosage During Low Blood Sugar
Persistent or recurring low blood sugar, known as hypoglycemia, is the most common situation where a person might consider reducing or holding their basal insulin. If blood glucose levels are consistently dropping below the target range of 70 mg/dL, especially overnight, it is a clear sign that the current basal dose may be too high. A long-acting dose that is too large can drive glucose down slowly over its 24-hour duration. The safest approach in this situation is typically reduction, not omission.
If a pattern of low blood sugar is identified, the recommended adjustment is a modest reduction in the daily dose. A common guideline is to decrease the total long-acting dose by approximately 10% or by one to two units, depending on the current total dosage. This adjustment should be made only after observing the pattern for several days to confirm it is not an isolated event caused by factors like unusual exercise or a missed meal.
If the scheduled injection time is approaching and you are currently experiencing a low blood sugar reading, the immediate priority is to treat the low first with fast-acting carbohydrates. Once the blood glucose level has stabilized and is rising, you can safely take your basal dose. Reducing the dose slightly in this circumstance may be appropriate, but taking the full dose is often necessary to prevent significant high blood sugar later in the day or night. Always consult your diabetes care team before making repeated or significant dose changes based on individual low readings.
Guidance for Illness and Fasting
Illness (Sick Days)
Illness, often referred to as a “sick day,” is a situation that significantly alters insulin requirements but rarely justifies stopping the long-acting dose. When the body is fighting an infection, flu, or other illness, it releases stress hormones like cortisol and adrenaline. These hormones work against insulin, causing the liver to dump extra glucose into the bloodstream, a phenomenon known as insulin resistance. This means that during an illness, a person often needs the same amount of basal insulin, or sometimes even more, to prevent severe hyperglycemia and DKA, even if they are not eating.
During a sick day, strict adherence to established “sick day rules” is necessary, which includes frequent blood glucose and ketone monitoring. If blood sugar levels are high or if moderate to large amounts of ketones are present, you must continue the full long-acting dose and supplement with extra rapid-acting insulin. You must ensure you are consuming enough fluids and carbohydrates, even liquid ones, to prevent dehydration and starvation ketosis.
Planned Fasting
Vomiting for more than a few hours is a sign of a worsening condition and requires immediate medical attention. The requirement for planned fasting, such as being designated NPO (nil per os) before a medical procedure or surgery, is one of the few instances where basal insulin dose reduction is commonly prescribed. Since the person will not be eating, the need for background insulin may decrease. However, stress from the procedure itself can still elevate blood sugar. In this specialized scenario, a healthcare provider or the hospital team will provide specific pre-procedure instructions, which often involve reducing the basal dose by 20% to 50% or transitioning to intravenous insulin management for the duration of the fast.
When to Consult a Healthcare Provider Immediately
While minor adjustments can be made with guidance, certain situations require prompt communication with a diabetes care team or immediate medical intervention. Any time you are uncertain about a dose adjustment, especially when managing long-acting insulin, it is safest to seek professional advice. Contact your healthcare provider if you observe a pattern of persistent high blood sugar or recurrent low blood sugar that does not resolve after two to three days of making small, guided adjustments. Call immediately if you are ill and unable to keep down food or fluids for more than four hours, or if you are persistently vomiting. The presence of moderate or large ketones in the blood or urine, combined with high blood sugar, also warrants an urgent call to your medical team. These signs indicate a lack of sufficient insulin and a high risk of developing DKA.