Hypoglycemia unawareness, also called impaired awareness of hypoglycemia (IAH), is one of the most distressing and dangerous problems people with diabetes can face. Normally, falling glucose triggers warning symptoms (like shaking or sweating) that push you to treat the low. With hypoglycemia unawareness, those warning signals are reduced or missing, so you may not realize you’re low until thinking, coordination, or behavior is already affected.

The good news: awareness can improve for many people. This page explains what hypoglycemia unawareness is, why it happens, how to recognize it, and practical steps to reduce risk—especially overnight.

What is hypoglycemia unawareness (impaired awareness of hypoglycemia)?

Impaired awareness of hypoglycemia means you don’t notice the usual early symptoms of low blood sugar, or you notice them only when glucose is already very low. Sometimes you may check a number that is clearly low and still feel “fine,” or feel too confused to act quickly.

This matters because early symptoms are your built-in safety alarm. Without them, lows are more likely to become severe (requiring help from another person).

Why it’s not a “willpower” problem

Hypoglycemia affects the brain. When the brain is under-fueled, insight and judgment can drop. That’s why people may deny they’re low, resist treatment, or behave in ways that feel out of character.

Why is hypoglycemia unawareness dangerous?

IAH is strongly linked to severe hypoglycemia. If you don’t feel a low coming on, you may keep driving, exercising, working, or sleeping while glucose continues to fall. Unless someone else recognizes what’s happening—or your CGM alarm wakes you—serious outcomes (including seizures or loss of consciousness) can occur.

Action step: If you’ve ever needed help from another person for a low, treat that as a major safety signal. Talk with your diabetes clinician promptly and review your insulin/medication plan.

What causes hypoglycemia unawareness?

The most common driver is repeated hypoglycemia. Frequent lows can “train” the body to respond less strongly—blunting the stress hormone response that usually triggers warning symptoms and helps raise glucose. Over time, lows can start to feel less dramatic… until they become severe.

Common triggers that can worsen awareness

Frequent recent lows (especially within the last 1–3 days)
Overnight lows (many people sleep through them)
Longer duration of diabetes (risk increases over time for many people)
Rapid drops (glucose falling quickly can outpace your ability to notice)
Alcohol within the last 12 hours (raises risk of delayed lows, especially overnight)
Exercise and increased activity (can increase insulin sensitivity for hours)
Some medications (for example, beta-blockers can mask certain warning signs like tremor or fast heartbeat)
Stress, burnout, depression, or low bandwidth for self-care (missed checks, missed snacks, dosing errors)

In type 1 diabetes, another factor is that the normal glucagon response to falling glucose is often reduced over time, which can further increase risk, making prevention and early detection even more important.

How common is impaired awareness of hypoglycemia?

Estimates vary depending on how it’s measured and who is studied. In type 1 diabetes, impaired awareness is commonly reported in a substantial minority of people (often cited in the range of up to ~40% in some studies and reviews). In older adults with type 1 diabetes, rates may be even higher. People with IAH have a meaningfully increased risk of severe hypoglycemia.

If you’re not sure whether this applies to you, treat it like a screening question: “Do I ever have lows without feeling them?” If yes, it’s worth addressing—even if severe lows haven’t happened yet.

What are the signs you might have hypoglycemia unawareness?

You don’t need a formal diagnosis to take this seriously. Common signs include:

You discover glucose is low (<70 mg/dL), but you have few or no symptoms
You frequently “suddenly realize” you are very low (rather than noticing early symptoms)
Others notice personality changes, confusion, or clumsiness before you do
You have nighttime lows (alarms don’t wake you, or you wake up “foggy”)
You’ve had a severe low (needed help, passed out, or had a seizure)

Can hypoglycemia unawareness be reversed?

Often, yes—at least partially. A widely recommended strategy is a period of strict avoidance of hypoglycemia. The goal is to give your body time to “reset” and re-learn early warning signals. Some people notice improvement within a few weeks, with further improvement over time if lows stay infrequent.

How do you restore low blood sugar awareness?

Use this as a practical plan to discuss with your clinician. You don’t have to do everything at once—small changes can make a big difference.

1) Raise targets temporarily (on purpose)

For a short period (often 1–3 weeks), set safer targets and aim to avoid lows completely.
This may include a higher CGM low alert (and an earlier “urgent low soon” style alert, if available).

2) Reduce the frequency of lows—especially after a low

After any meaningful low, be extra cautious for the next 24–48 hours.
Check more often, avoid aggressive corrections, and be conservative with activity and alcohol.

3) Use CGM alerts and share alarms if appropriate

If you’re at risk, a CGM is one of the most powerful tools for prevention—especially overnight.
Consider sharing alerts with a partner or family member if you sleep through alarms.

4) Review insulin settings (basal, carb factor, correction factor)

Frequent lows often mean insulin settings are too aggressive for your current needs.
Review patterns by time of day (overnight, after meals, after exercise).
Make stepwise changes with clinical guidance.

5) Use AID features strategically (if you have them)

Use exercise/activity modes when appropriate.
Be cautious with late corrections and “stacking” insulin.
If you’re frequently low, ask whether targets, insulin action time, or settings need adjustment.

What should you do to stay safe while you’re working on awareness?

Have a “severe low” plan (and supplies)

Keep fast carbs in multiple locations (bedside, car, desk, pocket).
Ask your clinician about glucagon. Today, there are easier-to-use options (including nasal and ready-to-use injectables) in addition to traditional kits.
Teach the people around you what to do if you can’t self-treat.

Driving safety

If you have impaired awareness, treat driving like a higher-risk activity:

Check glucose before driving and on long trips.
Don’t drive if you are low or if your blood glucose is rapidly dropping.
Keep fast carbs within reach (not in the trunk).

When should you call your clinician?

Contact your diabetes clinician promptly if:

You’ve had a severe low (needed help from another person)
You suspect impaired awareness (lows without symptoms)
You are having frequent lows (for example, more than 1–2 per week)
You’re waking up low or suspect overnight lows

You’re not “failing” if this happens. It usually means your insulin/medication plan needs to be updated to match real life.

Awareness can improve—start by avoiding lows

Hypoglycemia unawareness is common enough that many people encounter it at some point, especially with long-standing diabetes and repeated lows. The most effective path forward is usually straightforward: avoid hypoglycemia for a period of time, use CGM/AID tools and safer targets, and adjust insulin settings with your clinician so lows become rare. As lows decrease, warning symptoms often become clearer again—making life safer and less stressful.

Other Resources

Medical disclaimer: Educational content only. If someone is unconscious, having a seizure, or cannot swallow safely, call emergency services. Discuss frequent lows or suspected impaired awareness with your diabetes clinician.

Last Updated on December 18, 2025

Contents hide

1 What is hypoglycemia unawareness (impaired awareness of hypoglycemia)?

1.1 Why it’s not a “willpower” problem

2 Why is hypoglycemia unawareness dangerous?

3 What causes hypoglycemia unawareness?

3.1 Common triggers that can worsen awareness

4 How common is impaired awareness of hypoglycemia?

5 What are the signs you might have hypoglycemia unawareness?

6 Can hypoglycemia unawareness be reversed?

6.1 How do you restore low blood sugar awareness?

6.1.1 1) Raise targets temporarily (on purpose)