Written for Medical Realities by Meghan Gessner on August 29, 2025

Diabetes (aka diabetes mellitus) is what happens when your body can’t make or properly use insulin—the hormone that helps move sugar (glucose) from your blood into your cells for energy. The pancreas, a small organ tucked behind your stomach, is the insulin factory. When that system glitches, blood sugar stays high instead of getting used as fuel.

Why Diabetes Happens

No insulin at all.
Too little insulin.
Insulin resistance: your cells don’t “listen” to insulin the way they should, so glucose can’t get in.

Any of these can leave you with more sugar floating around in your bloodstream than your body can handle.

How Insulin Normally Works

You eat, your food breaks down into glucose, and that glucose heads into your bloodstream. Your pancreas senses the rise and releases insulin, which acts like a key to unlock your cells so glucose can get in and power everything you do.
If sugar dips too low, your body nudges you to eat and also releases backup glucose from your liver to keep you steady.

What “High Blood Sugar” Means

If your body isn’t making enough insulin—or your cells are resisting it—glucose piles up in your blood. That’s high blood sugar. Clinically, diabetes is diagnosed at a fasting blood glucose of 126 mg/dL or higher after not eating overnight.

How Common Is It in the U.S.?

About 38.4 million people in the U.S. have diabetes.
Roughly 8.7 million of them don’t know it yet.
Another ~97.6 million have prediabetes (blood sugar higher than normal but not in the diabetes range).

It’s a lifelong condition. There’s no cure right now, so the game plan is managing it—tracking blood sugar, dialing in food and activity, and using meds or insulin as needed. Tools like finger-stick meters and continuous glucose monitors help people (especially with type 1) figure out how much insulin they need and when.

Types of Diabetes

Type 1 Diabetes

This is the autoimmune one. Your immune system targets the pancreas’ beta cells (the insulin makers) and knocks them out. With zero natural insulin, you’ve gotta dose insulin by injection or pump to manage blood sugar.

Who it hits: often shows up before age 20, but it can start at any age—elementary school in Ohio or late 30s in California, it happens.
Why insulin matters: insulin is the “key” that lets glucose into your cells. No key = sugar stacks up in your bloodstream.

Type 2 Diabetes

Here, your body still makes insulin—but not enough, or your cells have insulin resistance and don’t respond well. Glucose can’t get into cells efficiently, so it builds up in the blood.

How common: it’s the most common diabetes type in the U.S., impacting tens of millions of Americans.
Who’s at risk: often over 40 and overweight, but it can affect folks who aren’t overweight, and it’s showing up more in kids and teens as obesity rises.
Complications to know: higher risk for vision loss, amputations, and chronic kidney failure needing dialysis.
Management options: many people improve numbers with weight loss, a balanced diet, and regular exercise. Others need oral meds that improve insulin action and/or insulin injections.

Prediabetes

Blood sugar is higher than normal but not yet in diabetes range—this stage is called prediabetes (impaired glucose tolerance).

How common in the U.S.: roughly 97.6 million adults.
Symptoms: usually none, which is why it flies under the radar.
Why it matters: it’s often the stepping-stone to type 2, and heart disease risk can start creeping up even here.
Next steps: ask your clinician about screening if you’ve got risk factors. Moving more, dialing in nutrition, and managing weight can delay or prevent type 2.

Gestational Diabetes

This type is triggered by pregnancy. Hormone shifts can make your body less responsive to insulin, pushing blood sugar up.

How common: occurs in up to about 9% of pregnancies in the U.S.
Why to watch it: good management during pregnancy supports health for both parent and baby, and it flags a higher future risk for type 2.

Gestational Diabetes: Who’s More at Risk

You’re more likely to develop gestational diabetes if you’re over 25, started pregnancy overweight, have a family history of diabetes, or belong to a group that’s been shown to have higher rates in U.S. data (including many Hispanic/Latino, Black, Native American, and Asian families). Risk isn’t destiny—just a heads-up to screen early and stay on top of it.

Screening During Pregnancy

Your OB team will screen you during pregnancy (usually with a glucose test). If blood sugar runs high and goes untreated, the odds of complications for you and the baby go up—so catching it early matters.

After Delivery: What Happens Next

Blood sugar usually slides back to normal within about 6 weeks after birth. Having had gestational diabetes does raise your future risk for type 2 diabetes, so plan on follow-up checks and long-game habits like movement, sleep, and balanced meals.

“Type 3 Diabetes” (What People Mean)

You may hear folks call Alzheimer’s disease “type 3 diabetes” because some research points to insulin resistance in the brain. That label isn’t official, and most clinicians don’t use it—it’s more of a theory than a diagnosis.

Other Diabetes Types to Know

Monogenic Diabetes

A set of rarer forms caused by single-gene changes passed down in families.

Neonatal diabetes: shows up in babies.
MODY (maturity-onset diabetes of the young): appears in older kids or young adults.
Treatment and testing depend on the specific gene involved.

Type 3c Diabetes

Can develop if the pancreas is removed or damaged (think severe pancreatitis, trauma, certain diseases). The pancreas makes insulin and digestive enzymes, so both blood sugar and digestion can be affected.

Secondary Causes

High blood sugar can also show up with:

Steroid medications (like long steroid courses)
Cystic fibrosis
Certain rare inherited conditions
Management focuses on the root cause plus blood-sugar control.

Diabetes Symptoms

Type 1: Comes On Fast

When type 1 hits, it can roll in suddenly and pretty hard. Watch for:

Extra thirst
Ravenous hunger
Dry mouth
Peeing a lot
Weight dropping for no obvious reason
Heavy fatigue (wiped out, low energy)
Blurry vision
Deep, labored breathing
Fainting or loss of consciousness (rare)

Type 2: Slow Burn (or No Obvious Signs)

Type 2 can look like type 1—but most folks either have no symptoms or they creep in slowly. You might notice:

Cuts/sores that take forever to heal
Itchy skin (often in the vaginal or groin area)
Rashes
Yeast infections
Numbness or tingling in hands and feet
Erectile dysfunction

Gestational Diabetes: During Pregnancy

Often there are no clear symptoms. If anything shows up, it’s usually:

More thirst
More frequent urination
Bigger appetite
Blurry vision

Pregnancy by itself can make you pee more and feel hungrier, so these signs don’t automatically mean gestational diabetes—but getting screened during pregnancy helps protect both you and your baby.

Diabetes Testing

Who should get checked

If you’ve got symptoms, don’t wait—get tested. Your doctor may also suggest screening if you’re higher risk. In the U.S., the USPSTF recommends screening adults 35–70 who have overweight or obesity.

How doctors confirm diabetes

Diabetes is diagnosed by measuring glucose in your blood. Most folks need two high results on different days to confirm it. Once diagnosed, regular checks help you keep numbers in range.

A1C (glycated hemoglobin)

What it shows: Your average blood sugar over ~2–3 months.
Numbers to know:
- 6.5% or higher → diabetes
- 5.7%–6.4% → prediabetes
FYI: You’ll repeat this test to see how your plan’s working.

Fasting Blood Sugar

Prep: Only water for 8 hours before the blood draw.
Numbers to know:
- 126 mg/dL or higher → diabetes
- 100–125 mg/dL → prediabetes

Random Blood Sugar

When it’s used: Anytime—no fasting. Handy if you’ve got clear symptoms and waiting isn’t safe.
Number to flag: 200 mg/dL or higher is considered too high.

Oral Glucose Tolerance Test (OGTT)

How it goes: Fast 8 hours, get a baseline blood draw, drink a very sweet liquid, then blood draws at 1 hour and 2 hours.
Numbers to know at 2 hours:
- 200 mg/dL or higher → diabetes
- 140–199 mg/dL → prediabetes
Pregnancy note: There’s a screening version that doesn’t require fasting for gestational diabetes; if it’s high, you’ll do a longer follow-up test.

Autoantibody Testing (Type 1 vs. Type 2)

What it checks: Immune system autoantibodies tied to type 1 diabetes.
When it’s used: If your sugar is high and your doctor needs to sort out type 1 vs. type 2, or if you’ve got a close family member with type 1.

Urine Ketone Test

Why it matters: Ketones show up when your body is burning fat instead of glucose (often from too little insulin). High ketones can signal diabetic ketoacidosis (DKA)—an emergency.
How it’s done: Pee in a cup, dip the strip, and the color change shows your ketone level.

Diabetes Tests — Practical Comparison for U.S. Patients
Test	What it measures	Prep & time	Typical use (U.S.)	Popularity	Accuracy / notes	Diagnostic cutoffs (adults, non-pregnant)	Pros	Cons
A1C (glycated hemoglobin)	Average blood glucose over ~2–3 months	No fasting; single blood draw; minutes	Screening, diagnosis, and ongoing monitoring	Very common	Stable, less day-to-day noise; can be skewed by anemia, hemoglobin variants, pregnancy, CKD	Diabetes: ≥6.5% Prediabetes: 5.7–6.4% Normal: <5.7%	Convenient; reflects long-term control	May misread with blood disorders; not great for rapid changes
Fasting Plasma Glucose (FPG)	Blood glucose at a single fasting time point	Fast 8 hours (water ok); quick draw	Screening and diagnosis; sometimes monitoring	Very common	Good specificity; some day-to-day variability; impacted by acute illness/meds	Diabetes: ≥126 mg/dL Prediabetes: 100–125 mg/dL Normal: <100 mg/dL	Simple, inexpensive	Requires fasting; single snapshot only
Random Plasma Glucose (RPG)	Blood glucose at any time (not fasting)	No prep; immediate result	Rapid check when symptoms are present	Common in urgent/clinic settings	Useful with classic symptoms; less specific without them	Diabetes: ≥200 mg/dL with classic symptoms (polyuria, polydipsia, weight loss)	Fast, no fasting needed	Not ideal for screening asymptomatic people
Oral Glucose Tolerance Test (OGTT, 75 g)	Body’s response to a measured glucose load over 2 hours	Fast 8 hours; baseline draw → drink 75 g glucose → draws at 1 & 2 hours (~2–3 hrs total)	Diagnosis of diabetes/prediabetes; sensitive for early dysglycemia	Less common (time-intensive)	High sensitivity; can vary with sleep, activity, meds; patient burden higher	2-hr value Diabetes: ≥200 mg/dL Prediabetes: 140–199 mg/dL Normal: <140 mg/dL	Detects impaired glucose tolerance that A1C/FPG can miss	Lengthy visit; sweet drink may cause nausea
Gestational 1-hr Glucose Challenge (50 g, non-fasting)	Screen for high glucose during pregnancy	No fasting; drink 50 g glucose; draw at 1 hr (~1 hr)	Routine pregnancy screening (U.S.)	Very common in OB care	Screen only—positives need a diagnostic OGTT; thresholds vary by clinic	Positive screen: ≥130–140 mg/dL (clinic-specific) → proceed to diagnostic OGTT	Easy to administer; catches most at-risk pregnancies	False positives; requires follow-up test
Autoantibody panel (e.g., GAD65, IA-2, ZnT8, IAA)	Immune markers suggesting type 1 diabetes	Standard blood draw	Differentiate type 1 vs. type 2/LADA	Used in specific cases	Helps classify etiology; not a glucose test	No glycemic cutoffs; reported as positive/negative (sometimes titers)	Guides treatment choice (insulin need)	Not for diagnosing diabetes by glucose criteria
Urine Ketone Test	Ketone bodies in urine (fat metabolism when insulin is low)	Dipstick at home/clinic; seconds to minutes	Assess risk of DKA; sick-day monitoring (esp. type 1)	Common for home use	Good for DKA risk; hydration can dilute results; blood ketones are more precise	Qualitative/semi-quantitative: negative / trace / small / moderate / large	Cheap, quick, widely available	Doesn’t diagnose diabetes; can lag behind blood ketones
Notes: U.S. diagnostic thresholds shown; many results require confirmation on a separate day. Lab methods and individual conditions (e.g., anemia, pregnancy, kidney disease, meds) can affect readings—your clinician will choose the best test and interpret results in context.

Diabetes Treatment

What You’re Aiming For

Steady blood sugar in your target range.
Healthy cholesterol & triglycerides (keep the heart happy).
Blood pressure under 130/80.
Delay or prevent complications (eyes, nerves, kidneys, heart).

How Treatment Gets Picked

Your plan depends on which type of diabetes you have. Most folks use a stack of meds + food strategy + movement + sleep/stress basics to keep numbers in check.

Keeping Tabs on Your Numbers

Type 1 (and some Type 2): check sugars several times a day—finger sticks or a CGM (continuous glucose monitor) that reads through the skin. Treat highs/lows fast.
Prediabetes & some Type 2: labs at checkups (anywhere from once to a few times a year), unless your clinician wants more frequent checks.

Meds You Might See

Insulin

Essential for Type 1 and used by many with Type 2. It lets glucose move from blood into cells.

How it’s taken: shots (syringe or pen) or an insulin pump that delivers tiny doses all day.
Timing: often around meals per your clinician’s plan.
Pregnancy: insulin is safe for gestational diabetes.

Oral Medications (Type 2)

Often one pill to start, then combinations if needed:

Metformin: turns down your liver’s glucose output and improves insulin sensitivity.
Sulfonylureas: nudge the pancreas to release more insulin.
SGLT2 inhibitors: help the kidneys dump extra glucose in urine.
DPP-4 inhibitors: raise levels of gut hormones that signal insulin release.
TZDs (thiazolidinediones): make cells more responsive to insulin.
Starch-slowing agents: delay carb breakdown so blood sugar rises more gently after meals.

GLP-1 & Dual GLP-1/GIP Receptor Agonists (Type 2)

These mimic natural gut hormones that boost insulin when you eat, slow stomach emptying, and turn down appetite in the brain. Result: smoother sugars and often weight loss.

How they’re taken: one is a pill; others are injections (daily or weekly).
FDA-approved GLP-1 RAs: dulaglutide, exenatide, liraglutide, lixisenatide, semaglutide.
Dual GLP-1/GIP RA: tirzepatide (the only approved dual agent).

Meds Beyond Blood Sugar

Your care team may stack a few “helper” meds to protect you from diabetes complications:

Blood pressure meds (like ACE inhibitors or ARBs) to keep numbers in check and help protect your kidneys and heart.
Cholesterol meds (often a statin) to lower LDL and cut heart risk.
Low-dose aspirin in select cases—only if your clinician says the benefit outweighs the bleeding risk.

Food, Timing, and Blood Sugar

Why meals matter

What you eat—and when you eat—can swing your glucose. Fast-digesting stuff (candy, soda, white bread, pastries) hits your bloodstream like a rocket. Skipping meals can tank your sugar too low.

If you have type 1

You’ll match insulin to carbs like a pro. That means:

Count carbs and learn your insulin-to-carb ratios.
Track how protein, fat, fiber, and timing shift your numbers.
Adjust doses based on meals, snacks, and activity—your provider will show you the playbook.

Smart plate for anyone with diabetes or prediabetes

Build meals that help steady sugars, lipids, and blood pressure:

Pile on produce: fruits and non-starchy veggies (think greens, peppers, berries).
Choose whole grains: oats, quinoa, brown rice, whole-wheat pasta/tortillas.
Lean proteins & dairy: poultry, fish, tofu, beans, low-fat yogurt/milk.
Nutrient-dense add-ins: foods rich in fiber, calcium, protein, and healthy fats (olive oil, nuts, seeds, avocado).

Things to limit

Sugary drinks and desserts
Alcohol (if you drink, know how it affects your glucose and meds)
Saturated fat (swap in unsaturated)
Sodium (check labels; restaurant food stacks up fast)
Refined grains (white bread, regular crackers, many pastries)

Move More, Control More

Why exercise helps

Activity improves insulin sensitivity, so your body uses glucose more efficiently. It also helps with blood pressure, cholesterol, and weight management.

The baseline target

150 minutes/week of moderate exercise (aim for ~30 minutes, 5 days/week).
Walk briskly, swim laps, cycle, dance—pick what you’ll actually do.
2 days/week of strength training for all major muscle groups.

Always clear new routines with your clinician, especially if you’re deconditioned or have heart/kidney/eye issues.

If you have type 1 (or insulin-treated type 2)

Prevent lows: you may need to reduce mealtime or basal insulin around workouts or take extra carbs (timing depends on the activity and your trend arrows if you use a CGM).
Keep quick carbs on you (glucose tabs/gel, juice box).
Check before/after (and sometimes overnight) until you learn your patterns.

Diabetes at Home: Your Day-to-Day Game Plan

Own Your Routine

You’ve got the wheel here. What you do between checkups makes the biggest difference for your numbers and how you feel.

Your At-Home Checklist

Follow your plan: take meds/insulin as prescribed and stick to the schedule.
Show up for checkups & labs: eyes, A1C, kidneys, cholesterol—keep those appointments.
Track at home: check blood sugar (and blood pressure if your doc asked).
Watch the hotspots: feet (cuts/blisters), gums (bleeding/soreness), and vision changes—flag issues early.
Stay vax’d: flu, RSV, and COVID-19—high blood sugar can dull immune defenses.
Work on weight if needed: even 5–10% down can help insulin work better.
Quit smoking: huge win for heart, kidneys, eyes, and nerves.
Manage stress: sleep, walks, breathing breaks, journaling—whatever keeps cortisol from spiking your sugar.

Be Ready for Lows (Hypo Game Plan)

Know your personal “low” number from your care team.
Keep fast carbs handy: glucose tabs/gel, 4–6 oz juice, regular soda, or hard candy.
Recheck in 15 minutes; repeat if still low. Eat a small snack if the next meal’s far off.

Preventing Type 2 Diabetes

What You Can and Can’t Prevent

You can’t prevent type 1, but you can lower your risk for type 2—and if you have prediabetes, you can often hit the brakes hard.

Food Moves That Help

Build your plate around veggies, fruit, whole grains, beans, lean proteins, and healthy fats (olive oil, nuts, avocado).
Cut the sugar bombs: soda/juice, desserts, refined grains (white bread, pastries).
Watch portions & timing: steady meals beat long fasts + giant spikes.

Move Your Body

Aim for 30 minutes of moderate activity, 5 days a week (brisk walk, cycling, swimming, dancing).
Add 2 days of strength training to boost insulin sensitivity.

Check Your Numbers

If you’re at higher risk, ask for blood sugar screening. Catching prediabetes early changes the whole story.

Meds That Can Help (Ask Your Doc)

Metformin may be recommended for some folks with prediabetes.
Weight-loss medications can support lifestyle changes if you qualify.

Quick Home Reminders

Set phone reminders for meds and glucose checks.
Keep a small kit in your bag/car: meter or CGM supplies, fast carbs, water.
Write down your targets (glucose, BP) and what to do if you’re out of range.

Diabetes — U.S. FAQ

What exactly is diabetes, in plain English?

It’s a problem with **insulin**, the hormone that moves sugar from your blood into your cells for energy. If you don’t make insulin (type 1) or your body doesn’t respond to it well (type 2), sugar builds up in your bloodstream and causes trouble over time.

How do type 1 and type 2 differ?

Type 1: autoimmune; pancreas makes little to no insulin. Needs insulin from day one.
Type 2: your body makes insulin but doesn’t use it well (insulin resistance) and may not make enough. Managed with lifestyle, pills, and sometimes insulin.

What symptoms should make me worry about diabetes?

Big thirst, peeing a lot, blurry vision, unexplained weight loss, fatigue. Type 2 can be sneaky with slow changes like slow-healing cuts, frequent infections, and tingling in hands/feet.

When should Americans get screened?

Adults **35–70** with **overweight or obesity** should be screened. Get checked sooner if you have risk factors (family history, prior gestational diabetes, certain health conditions).

Which tests diagnose diabetes and what are the numbers?

A1C: ≥ 6.5% (prediabetes 5.7–6.4%).
Fasting glucose: ≥ 126 mg/dL (prediabetes 100–125).
2-hr OGTT: ≥ 200 mg/dL (prediabetes 140–199).
Random glucose: ≥ 200 mg/dL with classic symptoms.

Usually you need confirmation on a separate day unless it’s clearly urgent.

What’s the day-to-day goal for my numbers?

Targets are personal, but many adults aim for an A1C near **7%**, blood pressure **<130/80**, and cholesterol in heart-healthy ranges. Your care team will set the exact goals for you.

How do food and timing affect blood sugar?

Fast carbs (soda, candy, white bread) spike you quick. Balanced plates (non-starchy veggies, lean protein, whole grains, healthy fats) smooth out the curve. Skipping meals can cause lows—especially if you use insulin or certain meds.

Which medications are commonly used in the U.S.?

Insulin: essential in type 1; used in some type 2.
Metformin and other oral meds (e.g., SGLT2, DPP-4, TZD).
GLP-1 and **dual GLP-1/GIP** injections (often weekly) that help sugars and appetite.
“Helper” meds: blood pressure and cholesterol drugs; low-dose aspirin in select cases.

What lifestyle changes move the needle the most?

Move more: ~150 minutes/week moderate exercise + 2 days of strength.
Sleep & stress: both affect insulin resistance—prioritize them.
Stop smoking: huge win for heart, kidneys, eyes, and nerves.
Weight loss: even 5–10% down can improve glucose control.

I have type 1—how do I avoid going low during workouts?

Plan ahead: consider adjusting insulin around exercise or take extra carbs. Keep fast carbs on you (glucose tabs, juice). Check before/after until you learn your patterns; CGMs help spot trends in real time.

What is DKA and when should I worry?

Diabetic ketoacidosis happens when there’s not enough insulin and your body burns fat fast, making ketones that can turn your blood acidic. Red flags: very high sugars, nausea/vomiting, deep breathing, fruity breath, confusion. Check ketones and seek urgent care.

Any U.S.-specific tips for insurance, supplies, and travel?

Insurance: ask about formulary switches and prior authorizations for insulin/CGMs.
Refills: set reminders; keep a backup meter, strips, and low supplies.
Travel: carry meds and devices in your **carry-on** with a letter if needed; pack extra.

How can I protect my eyes, feet, kidneys, and heart?

Eyes: yearly dilated exam.
Feet: daily checks; see a podiatrist for wounds or numbness.
Kidneys: yearly urine albumin and kidney labs.
Heart: keep BP, cholesterol, and A1C in target; stay active; don’t smoke.

I’m pregnant or planning—what should I know about gestational diabetes?

Pregnancy hormones can raise blood sugar even if you’ve never had diabetes. Screening is routine, and insulin is safe if needed. Most people return to normal after delivery, but long-term screening matters because future type 2 risk is higher.

General info for U.S. readers: use this as guidance, not a substitute for medical care. Your clinician can tailor targets, meds, and testing to your situation.

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