Diabetics need sugar when their blood glucose drops too low, a condition called hypoglycemia. This might seem contradictory since diabetes is often associated with high blood sugar, but the medications used to manage diabetes, especially insulin, can push blood glucose below 70 mg/dL. At that point, eating fast-acting sugar is the fastest way to prevent a medical emergency.
Why Blood Sugar Can Drop Too Low
Diabetes itself doesn’t cause low blood sugar. The treatments do. Insulin, whether injected or delivered by a pump, lowers blood glucose by moving it into cells. Certain oral diabetes medications also stimulate the pancreas to produce more insulin. In a person without diabetes, the body automatically dials back insulin production when blood sugar starts to fall. But injected insulin can’t be turned off once it’s in the body, and some medications keep working even when blood sugar is already dropping.
Several everyday situations can tip the balance: eating less than expected, delaying a meal, exercising more than usual, or accidentally taking too much medication. Alcohol can also lower blood sugar for hours after drinking. Any of these can create a mismatch between how much insulin is active in the body and how much glucose is available in the blood.
What the Body Needs Glucose For
Every cell in your body runs on glucose, but the brain is especially dependent. Despite making up only about 2% of body weight, the brain consumes roughly 20% of the body’s total energy. It burns glucose constantly, even during sleep or rest, to maintain the baseline electrical activity that keeps neurons responsive. Unlike muscles, which can switch to burning fat for fuel, the brain relies almost entirely on a steady supply of glucose from the bloodstream.
When that supply drops, the brain is the first organ to suffer. This is why the symptoms of low blood sugar are primarily neurological: confusion, difficulty concentrating, irritability, and in severe cases, seizures or loss of consciousness.
How Low Blood Sugar Feels
The body sends warning signals in a predictable sequence. The first wave of symptoms comes from the stress response: sweating, a racing heartbeat, trembling, anxiety, and sudden intense hunger. These early warning signs typically appear when blood sugar dips below 70 mg/dL, and they exist specifically to prompt the person to eat something.
If blood sugar continues to fall, the brain itself starts to malfunction. Confusion sets in, concentration becomes difficult, speech may slur, and behavior can seem erratic or irritable. Below about 54 mg/dL, the American Diabetes Association classifies the episode as clinically significant, the threshold where brain function is directly impaired and immediate action is required. At extremely low levels, below roughly 36 mg/dL, brain wave activity changes dramatically, and coma becomes a real risk.
One dangerous complication is that some people, particularly those who experience frequent lows, lose the ability to feel those early warning symptoms. Their body stops triggering the sweating and shaking that would normally alert them, so the first sign of trouble is confusion or disorientation, by which point they may already need help from someone else.
What Happens if Blood Sugar Stays Too Low
Prolonged severe hypoglycemia can cause lasting damage. When brain cells are starved of glucose, they begin to swell and die through a process driven by the buildup of toxic byproducts. The areas most vulnerable are the cerebral cortex, the hippocampus (critical for memory), and parts of the deep brain involved in movement. Extended episodes can result in permanent neurological deficits including paralysis on one side of the body, memory loss, or a persistent vegetative state. In the worst cases, untreated severe hypoglycemia is fatal.
This is the core reason diabetics carry sugar with them. It’s not a treat or a preference. It’s emergency medicine.
The 15-15 Rule for Treating a Low
The standard protocol is straightforward: eat or drink 15 grams of fast-acting carbohydrates, wait 15 minutes, then check blood sugar again. If it’s still below 70 mg/dL, repeat. Keep repeating until blood sugar returns to a safe range.
Fifteen grams of carbohydrates looks like:
- Four glucose tablets or one tube of glucose gel
- Half a cup (4 ounces) of fruit juice such as apple or grape (not diet or reduced-sugar)
- Half a can of regular soda (not diet)
- One tablespoon of sugar, honey, or corn syrup
The key word is “fast-acting.” Foods high in fat or protein, like a candy bar or peanut butter, slow digestion and delay the glucose from reaching the bloodstream. That delay matters when brain function is deteriorating by the minute. Pure glucose is the ideal choice because it requires no digestion at all and enters the blood almost immediately. Some diabetes medications that slow carbohydrate digestion make this distinction even more important. People taking those medications should use glucose tablets or gel specifically, since other carbohydrate sources won’t absorb quickly enough.
For people using automated insulin delivery systems (insulin pumps that adjust doses automatically), the recommended amount is smaller, typically 5 to 10 grams, since the pump will also reduce insulin delivery on its own.
Exercise and Preemptive Sugar
Physical activity makes muscles more sensitive to insulin and burns glucose faster. For someone on insulin or certain oral medications, this combination can cause blood sugar to drop during or even hours after a workout. Checking blood sugar before exercise is essential, and many people need a small carbohydrate snack beforehand to prevent a low. For longer activities like distance running or cycling, a combination of eating extra carbs and reducing medication doses is often necessary. This is another scenario where a diabetic “needs sugar,” not because their blood sugar is currently low but because it’s about to be.
When Sugar Isn’t Enough
If a person is too confused to eat, unable to swallow safely, losing consciousness, or not responding to repeated rounds of the 15-15 rule, the situation has moved beyond what oral sugar can fix. This is when glucagon becomes necessary. Glucagon is a hormone that signals the liver to release its stored glucose into the bloodstream. It comes in ready-to-use nasal sprays or auto-injectors designed so that a family member, coworker, or bystander can administer it without medical training.
People on insulin, especially those with type 1 diabetes, are generally advised to keep glucagon accessible and to make sure the people around them know where it is and how to use it. A person in a severe hypoglycemic episode cannot treat themselves.
Why It Seems Contradictory
The confusion makes sense. Diabetes is defined by blood sugar that’s too high, so needing sugar sounds like the opposite of what a diabetic should do. But the disease and its treatment create a narrow target: blood sugar needs to stay high enough to fuel the brain and low enough to avoid long-term damage to blood vessels, nerves, and organs. The medications that keep blood sugar from going too high can sometimes push it too far in the other direction. Sugar, in that moment, is the correction that keeps someone conscious and safe.