Can diabetes be missed in a blood test?

Diabetes is a serious condition that affects how your body handles glucose, resulting in high blood sugar levels. It can lead to many complications if left untreated. That’s why regular screening through blood tests is so important – it can catch diabetes early before complications set in. But can diabetes sometimes slip through the cracks and be missed on routine blood work? Let’s take a closer look.

Can diabetes be missed on a fasting blood glucose test?

A fasting blood glucose test is one of the most common screening tools for diabetes. It measures your blood sugar after an 8 to 12 hour fast. A level below 100 mg/dL is normal, 100 to 125 mg/dL indicates prediabetes, and 126 mg/dL or higher on two separate tests means you have diabetes.

For the most part, fasting blood glucose is an accurate test that will catch diabetes. However, it’s not perfect:

– Up to one-third of people with diabetes have normal fasting blood sugar in the early stages. This is more common in type 2 diabetes.
– Blood sugar can fluctuate day-to-day. An unusually low reading during screening could miss diabetes that’s actually present.
– Certain medical conditions like pregnancy or pancreatic disease can affect blood sugar readings.

So while fasting blood glucose is a convenient first-line test, it’s not foolproof. Diabetes can sometimes go undetected, especially early type 2 disease.

Can the A1C test miss diabetes?

The A1C is another common blood test used to diagnose diabetes. It measures your average blood sugar over the past 2 to 3 months by looking at how much sugar is bound to hemoglobin in red blood cells.

An A1C below 5.7% is normal, 5.7% to 6.4% indicates prediabetes, and 6.5% or higher means you have diabetes.

The A1C has some advantages over fasting blood glucose:

– It gives a better picture of blood sugar over time instead of a single point.
– It’s more convenient as fasting isn’t required.

But the A1C also has limitations:

– It can miss early cases of diabetes where blood sugar spikes are still intermittent.
– Certain medical conditions like anemia can interfere with the results.
– Vitamins like C and E can also affect readings.

Overall, the A1C is a very helpful test. But mild or early diabetes can potentially be overlooked, so it should not be relied on alone.

How often are cases of diabetes missed?

It’s difficult to put an exact number on how frequently diabetes is missed. However, studies looking at undiagnosed diabetes estimate:

– Around 25% of people with diabetes in the U.S. are undiagnosed.
– Up to 90% of cases may be missed in prediabetes.
– Type 2 diabetes can go undiagnosed for up to 10 years or longer before symptoms bring someone in for testing.

The risks of missing diabetes include uncontrolled blood sugar leading to complications like neuropathy, kidney disease, cardiovascular disease, nerve damage, and vision loss. That’s why experts recommend re-screening every 1-3 years for people at high risk. This helps ensure diabetes gets picked up in a timely manner.

Who is at risk of a missed diagnosis?

There are certain risk factors that make it more likely diabetes could be missed or overlooked:

– Being overweight or obese
– Physical inactivity
– Family history of diabetes
– History of gestational diabetes or giving birth to a large baby
– Polycystic ovary syndrome (PCOS)
– High blood pressure
– Abnormal cholesterol levels
– Age over 45 years
– Racial backgrounds like African American, Hispanic/Latino, American Indian, Asian American, or Pacific Islander

People with any of these risk factors should be especially diligent about getting routine screening. Undiagnosed diabetes is more common in minority groups and the elderly as well.

How can missed diabetes be detected?

If you’re concerned your diabetes may have been missed, there are a few strategies to help detect it:

– Get retested annually or semi-annually if you have risk factors
– Ask your doctor about a oral glucose tolerance test which measures blood sugar before and after a sugar drink
– Check for signs of prediabetes like darkened skin patches or blurry vision
– Monitor blood sugar at home fasting and after meals
– Get an A1C test at least twice per year to complement fasting blood glucose
– Pay attention to increased thirst, frequent urination, fatigue, and unexplained weight loss

Listen to your body and be proactive with your healthcare provider. Push for additional testing if diabetes is suspected – early detection makes a huge difference.

Can Pre-diabetes Be Missed on a Test?

Prediabetes is a condition where blood sugar levels are higher than normal but not yet high enough for a diagnosis of type 2 diabetes. Can prediabetes go undetected on common screening tests?

Challenges detecting prediabetes

Prediabetes is easy to miss for a few reasons:

– Up to 90% of people with prediabetes are unaware they have it.
– It usually has no obvious symptoms that prompt testing.
– Only routine screening uncovers most cases.
– People can have prediabetes for many years before it progresses to diabetes.

This “in-between” state means it flies under the radar more than full-blown diabetes. However, detecting prediabetes is critical for preventing type 2 diabetes down the road through lifestyle changes.

Fasting blood glucose misses most prediabetes

The fasting blood glucose test described earlier only detects about 30% of prediabetes cases. It misses the other 70% who have normal fasting blood sugar but elevated post-meal levels.

A1C also misses many prediabetes cases

The A1C does a bit better, detecting around 50% of people with prediabetes. But it still misses a significant number of cases.

Oral glucose tolerance test is optimal

The best test for prediabetes is the oral glucose tolerance test (OGTT). It measures blood sugar while fasting, and again 2 hours after drinking a glucose solution.

The OGTT picks up about 90% of prediabetes cases, making it the gold standard. It’s better than A1C or fasting glucose alone at assessing risk for future diabetes in someone with borderline blood sugars.

Who should get tested for prediabetes?

Because routine blood tests often miss prediabetes, experts recommend screening for people at high risk. This includes those who are:

– Overweight or obese
– Age 45 or older
– Physically inactive
– Have immediate family members with diabetes
– Have a history of gestational diabetes or gave birth to a large baby
– Are African American, Hispanic/Latino, American Indian, Asian American or Pacific Islander
– Have high blood pressure, cholesterol problems, or polycystic ovary syndrome

Women with a history of gestational diabetes should get lifetime screening for prediabetes every 1-3 years after delivery. Early detection in high risk groups gives the best chance to make lifestyle changes to prevent diabetes.

Risks of Missing Diabetes or Prediabetes

Failure to detect diabetes or prediabetes can allow complications to develop silently over months and years. What are some of the risks?

Cardiovascular damage

Elevated blood glucose from diabetes or prediabetes can start damaging blood vessels and nerves leading to the heart. It accelerates atherosclerosis, or hardening of the arteries. This raises the likelihood of a heart attack or stroke before diabetes is diagnosed.

Nerve injury (neuropathy)

Excess blood sugar can injure the walls of the capillaries that nourish the nerves. This causes nerve damage known as diabetic neuropathy. Poor sensation and pain can result, often in the feet, legs or hands. Neuropathy is one of the most common complications.

Kidney problems (nephropathy)

The kidneys are another area prone to damage from uncontrolled diabetes. It constricts and thickens the small arteries around the kidney’s filtering units. This can lead to chronic kidney disease and even renal failure over time if blood sugar is not controlled.

Vision loss (retinopathy)

High blood sugar from diabetes stresses the tiny blood vessels in the eyes. It can cause them to leak fluid and blood leading to blurry vision, spots, floaters and blindness. Diabetes is the leading cause of acquired blindness in adults.

Foot wounds

Numbness in the feet makes it easy for people with diabetes to injure their feet without noticing. Small cuts and blisters can develop into major infections and ulcers due to poor circulation. This complication often leads to hospitalization.

Frequent infections

Elevated blood sugar weakens the immune system and makes people with diabetes more vulnerable to illnesses. Bacterial and fungal infections are more common and severe, especially bladder infections, vaginal infections in women, and skin infections.

Lifestyle Changes to Prevent Diabetes

If you’ve been diagnosed with prediabetes or have risk factors, you may be able to avoid developing diabetes through lifestyle measures:

Lose excess weight

Shedding just 5-10% of your body weight can help get your blood sugar under control. Aim to achieve and maintain a healthy body mass index (BMI).

Exercise regularly

Get moving with 150 minutes per week of moderate activity like brisk walking. This helps improve insulin sensitivity and lowers blood sugar levels. Strength training 2-3 times a week provides added benefits.

Follow a healthy diet

Choose foods like vegetables, fruits, whole grains, legumes, lean proteins and healthy fats. Limit sugar, refined grains, fried foods and red meat. Portion control is also key.

Quit smoking

Kicking the cigarette habit lowers your diabetes risk. Smoking worsens insulin resistance. Speak to your doctor about safe and effective smoking cessation techniques.

Limit alcohol intake

Heavy alcohol use promotes insulin resistance and inflammation. Men should stick to no more than 2 drinks per day, and women 1 drink daily.

Don’t get discouraged! Small, sustainable changes to your daily habits can get your blood sugar under control and prevent progression to type 2 diabetes. Consult a nutritionist or diabetes educator for guidance.

Medical Interventions Besides Lifestyle Changes

If lifestyle measures alone don’t lower your blood sugar enough, certain medications and supplements can help manage prediabetes:


Metformin is the first-line drug to treat prediabetes. It lowers blood glucose levels by reducing liver glucose production and enhancing insulin sensitivity.

GLP-1 agonists

Injectable GLP-1 medications like liraglutide (Victoza) stimulate insulin release and suppress appetite. They may help some people shed pounds.

Alpha-glucosidase inhibitors

Drugs like acarbose (Precose) and miglitol (Glyset) slow digestion of carbohydrates in the small intestine to minimize post-meal blood sugar spikes.

Bariatric surgery

Weight loss (bariatric) surgery like gastric bypass and sleeve gastrectomy can effectively treat prediabetes in obese individuals when lifestyle changes aren’t enough.


Berberine is a supplement that works similarly to metformin, enhancing insulin sensitivity and lowering blood sugar. It also benefits cholesterol.


A mineral that enhances insulin activity. May help control blood glucose in some prediabetes patients. More research is needed.


May mimic insulin and help regulate blood sugar levels. However, meta-analyses show effects are minor and short-term. Should not replace standard medical therapies.

Consult your healthcare provider about adding these treatments to lifestyle changes if your prediabetes is not well-controlled through diet and exercise alone.

Preventing Missed Diagnoses

What key steps can you take to reduce the likelihood that diabetes gets overlooked? Here are some tips:

Get annual diabetes screening

Adults age 45 and up should be screened annually for diabetes and prediabetes through tests like fasting glucose, A1C, or oral glucose tolerance. Earlier screening is recommended for overweight individuals or those with risk factors.

Repeat testing is crucial

Don’t rely on a single normal blood sugar reading, especially if you have symptoms or risk factors. Follow up with repeat testing over time to rule out intermittent spikes.

Discuss all your risk factors

Clearly convey your personal and family history to your provider so they can make informed decisions about screening frequency. Mention any symptoms you’ve noticed as well.

Learn diabetes warning signs

Look out for increased thirst/urination, fatigue, blurry vision, wounds that won’t heal, tingly hands/feet, and unexplained weight loss. Monitoring blood sugar at home provides added data between visits.

See your eye doctor annually

Eye exams can detect early diabetic retinopathy before noticeable vision changes occur. Make dilated eye exams part of your routine care.

Being proactive with screening and knowing your risks are key to avoiding delayed or missed diagnoses of diabetes and prediabetes. Partner closely with your healthcare team and stay vigilant about monitoring blood sugar. Early detection makes all the difference in preventing devastating complications.


Diabetes is an extremely common condition affecting millions worldwide. But cases can still be missed during routine screening through fasting glucose and A1C tests, especially early type 2 disease and prediabetes. Certain high risk groups like the elderly and minorities may face the greatest chance of slipping through the cracks undiagnosed.

Going undetected allows diabetes to cause silent damage to the heart, nerves, kidneys and eyes. That’s why those at risk require diligent annual re-screening to detect subtle changes in blood sugar before complications occur. Monitoring for symptoms and getting multi-faceted testing is also key. With proper screening and early diagnosis, diabetes can be managed effectively to prevent its most devastating consequences. Work closely with your healthcare provider to ensure any borderline cases don’t get overlooked.

Leave a Comment