Hypoglycemia vs. Hyperglycemia: Key Differences Patients Should Understand

Glucose that’s too low (hypoglycemia) or too high (hyperglycemia) can lead to urgent problems now and serious health issues later. Knowing the differences, recognizing early signs, and acting quickly can prevent ER visits, improve daily energy and mood, and protect your heart, eyes, kidneys, nerves, and brain. This guide is for anyone living with diabetes or prediabetes, and for their family, friends, coworkers, teachers, and caregivers.

Understanding blood glucose levels is crucial for anyone living with diabetes or prediabetes, as both hypoglycemia (low blood sugar) and hyperglycemia (high blood sugar) can lead to immediate health risks and long-term complications. Recognizing early warning signs and taking swift action can prevent emergency situations, enhance energy levels, improve mood, and protect vital organs such as the heart, eyes, kidneys, nerves, and brain. This guide serves as a valuable resource for individuals affected by these conditions and their support networks, ensuring everyone is equipped with the knowledge necessary to manage glucose levels effectively.

Why understanding lows and highs matters for your health

Glucose powers your brain and body. When levels drop too low, your brain doesn’t get enough fuel, which can impair thinking, coordination, and judgment within minutes. Very low levels can cause seizures, coma, or death if not treated rapidly.

When glucose runs high for hours to days, you may feel tired, thirsty, and unwell. Sustained high levels increase the risk of infections and, over months to years, cause damage to eyes, kidneys, nerves, heart, and blood vessels. Very high levels—especially with ketones—can lead to diabetic ketoacidosis (DKA) or, in type 2 diabetes, hyperosmolar hyperglycemic state (HHS), both medical emergencies.

Understanding symptoms, triggers, and action steps helps you stay in range more often and live safely and confidently.

What counts as hypoglycemia: definition and target ranges

• Hypoglycemia is typically defined as a blood glucose under 70 mg/dL (3.9 mmol/L).
• Clinically significant hypoglycemia is under 54 mg/dL (3.0 mmol/L).
• Severe hypoglycemia means you need help from another person because of confusion, unconsciousness, or seizure—regardless of the exact glucose number.
• Common daily targets for many nonpregnant adults: 80–130 mg/dL (4.4–7.2 mmol/L) before meals; less than 180 mg/dL (10.0 mmol/L) 1–2 hours after meals. Targets are individualized.

What counts as hyperglycemia: definition and target ranges

• Hyperglycemia generally means glucose over 180 mg/dL (10.0 mmol/L), especially 1–2 hours after eating.
• Fasting levels persistently above 126 mg/dL (7.0 mmol/L) suggest diabetes.
• For many using insulin, checking for ketones is recommended when levels are above about 250 mg/dL (13.9 mmol/L), especially if you feel ill.

Who is most at risk for lows, highs, or both

People at higher risk for lows include those using insulin or sulfonylureas; individuals with impaired kidney or liver function; older adults; people with previous severe lows or hypoglycemia unawareness; and those who drink alcohol on an empty stomach. Highs are more common during illness, with missed medications or pump/site issues, when taking steroids, with high-carb meals, or during major stress. Pregnant people and those with type 1 diabetes are at risk for both extremes.

Symptoms you can feel: hypoglycemia vs. hyperglycemia at a glance

• Hypoglycemia (low):
  • Shakiness, sweating, fast heartbeat, hunger
  • Anxiety, irritability, tingling lips or fingers, pale skin
  • Headache, dizziness, blurred vision
  • Confusion, clumsiness, behavior changes; severe lows can cause seizures or unconsciousness
• Hyperglycemia (high):
  • Increased thirst and urination, dry mouth
  • Fatigue, blurry vision, headaches
  • Nausea; abdominal pain (especially with ketones)
  • Fruity breath, deep/rapid breathing, confusion or drowsiness at very high levels

Hidden signs you might miss: cognitive, mood, and physical clues

• Hypoglycemia:
  • Trouble concentrating, slowed thinking, sudden mood swings
  • Nightmares, night sweats, waking with headache
  • Reduced awareness of symptoms after frequent lows
• Hyperglycemia:
  • Brain fog, irritability, decreased school/work performance
  • Recurrent yeast or urinary tract infections, slow-healing cuts
  • Leg cramps, dehydration, unintentional weight loss with very high levels

Common triggers of hypoglycemia: medications, meals, activity, alcohol

• Too much insulin or sulfonylurea for the food eaten
• Delayed or skipped meals/snacks; eating fewer carbs than planned
• More physical activity than usual; late-day exercise without adjusting insulin/carbs
• Alcohol (especially without food), which can suppress liver glucose release overnight
• Hot baths/saunas, weight loss, improved kidney function, or new medication interactions

Common triggers of hyperglycemia: illness, stress hormones, missed doses, carbs

• Illness, infection, surgery, pain, or steroids (e.g., prednisone)
• Missed or delayed insulin or other diabetes medications
• Insulin pump infusion set failures, air bubbles, or site scarring
• Large or high–glycemic index meals; grazing
• Hormonal changes (dawn phenomenon, menstrual cycle), intense mental stress, dehydration

How to check your glucose: meters, CGM, and when to test

Glucose meters give a real-time fingerstick number and are reliable when used correctly. Continuous glucose monitors (CGMs) track trends and provide alerts, but can lag 10–20 minutes behind blood glucose, especially during rapid changes.

Consider testing:

• Before meals and snacks, at bedtime, before driving, and before/after exercise
• When you feel symptoms of low or high
• More often when ill, starting a new medication, after site changes, or when readings don’t match how you feel
• With CGM, confirm with a fingerstick if the reading seems wrong, is rapidly changing, or before treating a suspected low or giving a large correction dose

Interpreting your numbers: thresholds for action and personal targets

Discuss personal targets with your clinician. Many adults aim for 70–180 mg/dL most of the time. Plan specific thresholds for action, such as treating at 70 mg/dL on the way down, checking ketones at 250 mg/dL if you have type 1 diabetes or are ill, and calling for help if severe symptoms occur. Older adults, children, and pregnant people often have different targets.

Immediate steps for hypoglycemia: fast-acting carbs, the 15-15 rule, glucagon

• Treat immediately if under 70 mg/dL or if symptomatic and you cannot check:
  • Take 15 grams of fast-acting carbs (e.g., glucose tablets, 4 oz/120 mL juice or regular soda, glucose gel). Avoid chocolate or high-fat foods—they act too slowly.
  • Wait 15 minutes, recheck. If still under 70 mg/dL, repeat 15 g of carbs.
  • Once back above 70 mg/dL and more than 30–60 minutes until your next meal, eat a small snack with carbs and protein to prevent another drop if advised in your plan.
• If you are unconscious, having a seizure, or unable to safely swallow:
  • Another person should give glucagon (nasal or injection) and call emergency services. Do not give food or drink by mouth to an unconscious person.
  • Place the person on their side to prevent aspiration.

Immediate steps for hyperglycemia: hydration, correction insulin, ketone checks

• Check glucose and consider ketones if above about 250 mg/dL, you feel ill, or you have type 1 diabetes.
• If ketones are negative/small and you use insulin:
  • Give a correction dose per your plan.
  • Drink water or sugar-free fluids; walk lightly if no ketones.
  • Recheck in 2–3 hours; change pump site if levels do not fall as expected.
• If ketones are moderate to large or you’re vomiting, breathing fast, or very drowsy:
  • Give ketone correction per plan, hydrate, and seek urgent medical advice; go to emergency care if unable to keep fluids down or levels are not improving.

When you’re not sure if it’s low or high: safe actions to take first

• Check your glucose immediately. If you cannot check:
  • Treat as low with 15 g fast-acting carbs, because hypoglycemia is more immediately dangerous.
  • Do not give insulin until you confirm a high.
  • Ask someone to stay with you and recheck within 15 minutes.

Special situations: exercise, driving, sleep, and alcohol

Before planned exercise, check glucose, consider reducing insulin or adding carbs, and use CGM alerts if available. Avoid intense exercise if glucose is high with moderate/large ketones. For driving, ensure glucose is safely above about 90 mg/dL and rising; keep fast carbs in the vehicle. Overnight, consider lower alerts on CGM, bedtime checks, and basal adjustments if you have frequent nocturnal lows. Alcohol increases delayed hypoglycemia risk—eat carbs, limit intake, and set overnight alerts.

Sick-day rules: preventing DKA and managing highs during illness

During illness, stress hormones raise glucose and increase ketone risk. Keep taking basal insulin even if not eating. Check glucose every 2–4 hours and ketones every 4–6 hours if levels run high. Sip fluids regularly; include carbs if you cannot eat solid food. Seek medical care for persistent vomiting, large ketones, shortness of breath, or glucose staying over about 300 mg/dL despite extra insulin.

Medication considerations: insulin, sulfonylureas, SGLT2s, and other therapies

Insulin and sulfonylureas (e.g., glyburide, glipizide) can cause hypoglycemia. Meglitinides can as well. Metformin, GLP-1 receptor agonists, DPP-4 inhibitors, and thiazolidinediones rarely cause lows on their own but can when combined with insulin or sulfonylureas. SGLT2 inhibitors reduce glucose but can increase the risk of euglycemic DKA, particularly in type 1 diabetes or during illness, fasting, or low-carb diets. Steroids raise glucose; beta-blockers can mask some low symptoms (like a fast heartbeat). Review all medications and supplements with your care team.

Type 1, type 2, and gestational diabetes: what differs in managing lows and highs

People with type 1 diabetes depend on insulin and have high risk for DKA with missed doses or illness; they also face higher hypoglycemia risk. Many with type 2 diabetes experience hyperglycemia more commonly early on; severe highs can progress to HHS during illness or dehydration. Gestational diabetes requires tighter targets to protect the baby; even modest highs may need action, and hypoglycemia prevention is a priority when insulin is used.

Children, older adults, and pregnancy: tailored safety tips

Children may not recognize or communicate symptoms; caregivers and school staff should be trained to treat lows and use glucagon. Older adults have higher risk of severe hypoglycemia and falls; targets are often relaxed to prioritize safety. Pregnancy often uses tighter ranges and more frequent monitoring; ketone checks and rapid contact with the obstetric and diabetes team are essential when levels are high.

Preventing future episodes: meal timing, dose adjustments, and routine planning

• Match insulin/sulfonylurea doses to your meals and activity; adjust ratios and correction factors with your clinician.
• Pre-bolus mealtime insulin (often 10–20 minutes) when safe; delay if starting low.
• Plan carbs for exercise and after alcohol; consider insulin reductions.
• Rotate injection or infusion sites and change pump sets on schedule.
• Use CGM alerts, review patterns weekly, and update your plan after any severe event.

Building a personal action plan and wearing medical ID

Create a written plan that defines your targets, when to treat, how much carbohydrate to use, how to correct highs, when to check ketones, and when to call for help. Keep fast carbs and glucagon accessible at home, work, school, and in your bag. Wear a medical ID that states your diagnosis, insulin use, allergies, and an emergency contact.

When to call your care team—and when to seek emergency care

• Call your care team for:
  • Frequent lows or highs, new or worsening symptoms, dose questions, or recurring nighttime issues
  • Illness requiring medication changes (e.g., steroids) or persistent ketones
• Seek emergency care now for:
  • Severe hypoglycemia (seizure, unconsciousness), or if glucagon is required
  • Moderate/large ketones with vomiting, abdominal pain, or rapid breathing
  • Signs of HHS: extreme thirst, confusion, weakness, very high glucose with dehydration

How family, friends, and coworkers can support you

• Learn to recognize low and high symptoms and where you keep glucose and glucagon.
• In a severe low, give glucagon and call emergency services; place the person on their side. Do not give food or drink by mouth if not fully awake.
• Encourage regular meals, breaks to check glucose, and hydration during busy days.
• Respect privacy while supporting safety; ask how you can help according to the person’s plan.

Tech and tools that help: CGM alerts, pumps, smart pens, and apps

CGMs with customizable alerts and data sharing can catch trends early. Insulin pumps and automated insulin delivery systems can reduce time spent high and low. Smart pens track doses and timing to prevent stacking. Mobile apps help log food, activity, and symptoms, and can integrate with devices to support pattern recognition and team-based care.

Myths, mistakes, and how to avoid them

• Treating lows with chocolate or high-fat foods—use fast glucose instead.
• “Stacking” correction insulin too soon—wait the recommended time per your plan.
• Exercising through high glucose with ketones—this can worsen ketones; address first.
• Assuming CGM is always exact—confirm when readings don’t match symptoms.
• Skipping insulin during illness—continue basal insulin and follow sick-day rules.

Questions to bring to your next appointment

• What are my personal glucose targets and action thresholds?
• How should I adjust doses for exercise, illness, or alcohol?
• When should I check ketones, and what is my ketone correction plan?
• Which medications raise my risk of lows or DKA, and how can I reduce that risk?
• Is CGM, a pump, or a smart pen appropriate for me?
• How can we simplify my regimen to minimize extremes?

Trusted resources and support communities

• Mayo Clinic: Hypoglycemia — https://www.mayoclinic.org/diseases-conditions/hypoglycemia/symptoms-causes/syc-20373685
• Mayo Clinic: Hyperglycemia — https://www.mayoclinic.org/diseases-conditions/hyperglycemia/symptoms-causes/syc-20373647
• MedlinePlus: Low blood sugar — https://medlineplus.gov/ency/article/000386.htm
• MedlinePlus: High blood sugar — https://medlineplus.gov/ency/article/000304.htm
• CDC: Managing blood sugar — https://www.cdc.gov/diabetes/managing/managing-blood-sugar.html
• Healthline: Diabetic ketoacidosis — https://www.healthline.com/health/diabetic-ketoacidosis
• WebMD: Hypoglycemia overview — https://www.webmd.com/diabetes/low-blood-sugar-hypoglycemia
• American Diabetes Association Standards of Care — https://diabetes.org/standards

FAQ

• Can I rely on my CGM for lows? CGM is excellent for trends and alerts, but can lag behind blood glucose. If you have symptoms, the reading seems wrong, or the value is rapidly changing, confirm with a fingerstick before making big treatment decisions.

• How much carbohydrate treats a mild low? Start with about 15 grams of fast-acting carbs, then recheck in 15 minutes. Repeat if still low. Children may need weight-based amounts—ask your clinician for a tailored plan.

• Can protein or fat treat hypoglycemia? No. Protein and fat digest slowly and won’t raise glucose fast enough. Use glucose tablets, juice, regular soda, or glucose gel.

• Should I exercise if my glucose is high? If glucose is high without ketones, light activity can help lower it. If ketones are moderate or large, avoid exercise and follow your ketone plan—exercise can worsen ketones.

• What is euglycemic DKA with SGLT2 inhibitors? It’s DKA with normal or only mildly elevated glucose, seen rarely with SGLT2 inhibitors. Risk rises during illness, fasting, low-carb diets, or perioperatively. Know sick-day rules and when to stop these medicines temporarily.

• Do repeated lows cause harm? Frequent hypoglycemia can impair awareness of symptoms and may affect cognition and heart rhythm. Work with your team to reduce episodes and adjust targets if needed.

• Why are my mornings high? The dawn phenomenon (early-morning hormones) can raise glucose. Solutions include basal insulin adjustments, pump settings, or evening medication timing—review patterns with your clinician.

• Can stress really raise glucose? Yes. Stress hormones increase glucose output and insulin resistance. Hydration, activity, sleep, and stress-reduction techniques can help, along with dose adjustments per your plan.

If this guide helped you understand the differences between hypoglycemia and hyperglycemia, share it with someone who might benefit. Bring your questions to your healthcare provider to tailor an action plan, and explore related patient-friendly articles and tools on Weence.com to support your day-to-day diabetes care.