A normal person’s glucose line on a graph typically shows small, gradual fluctuations in blood sugar levels throughout the day. Here’s what it generally looks like:

  1. Fasting state (morning before eating): Blood sugar is usually stable and low, around 70-99 mg/dL.

  2. After meals (postprandial spikes): Blood sugar rises after eating, peaking about 1-2 hours after a meal but usually stays below 140 mg/dL. The rise is moderate and then returns to normal within a couple of hours.

  3. Between meals: Blood sugar gradually decreases and stabilizes in a narrow range.

  4. Nighttime: Blood sugar remains relatively stable overnight, with only small variations depending on fasting duration.

The graph would show gentle rises after meals and smooth drops between meals without sharp spikes or drops typical of those with diabetes. There’s no dramatic or erratic movement unless influenced by intense activity or other factors.

When we say that blood sugar returns to “normal” within a couple of hours after eating, it generally means that blood glucose levels return to a range that is close to fasting levels, but not necessarily exactly the same as fasting glucose.

Here’s the breakdown:

  • Fasting glucose: Typically 70-99 mg/dL.
  • Postprandial (after eating): Blood sugar usually peaks about 1-2 hours after eating, but should remain below 140 mg/dL in non-diabetic individuals.
  • 2 hours after eating: By this time, blood sugar typically returns to the 70-120 mg/dL range. It may not be exactly the same as fasting glucose, but it should be close, generally below 120 mg/dL.

In a healthy individual, the body efficiently clears excess glucose from the blood after meals, bringing levels back to this general range.

Is ‘normal’ only a representation sampling of people on the standard American Diet (SAD) and not necessarily healthy or optimal?
The typical “normal” blood glucose levels—such as fasting glucose between 70-99 mg/dL and postprandial glucose under 140 mg/dL—are based on a broad population sampling, which includes people eating the Standard American Diet (SAD) as well as other diets. These ranges are considered representative of the average healthy population, but they reflect what is commonly observed in people who may not follow an optimal diet.

Here’s how to break it down:

  • Healthy People: Many individuals who are considered metabolically healthy, even if they eat a standard diet, tend to fall within these “normal” ranges. However, their blood sugar may still fluctuate more after meals, especially if they consume high-carb or processed foods. While they don’t have diabetes, they might experience higher spikes compared to someone on a low-carb or nutrient-dense diet.

  • Standard American Diet (SAD): This diet, which is typically high in refined carbohydrates and sugars, can lead to greater variability in blood glucose levels. Many “healthy” people on the SAD might have blood sugars at the upper end of these normal ranges (e.g., 99 mg/dL fasting, 130-140 mg/dL post-meal), but they aren’t classified as having diabetes. However, this doesn’t necessarily mean their glucose control is optimal.

In contrast, people following a low-carb or ketogenic diet, as Dr. Bernstein advocates, often have lower and more stable blood glucose levels because of reduced glucose intake and improved insulin sensitivity. So, while the typical ranges are deemed healthy by conventional standards, they may not reflect the tight control or lower variability seen in those following a stricter, low-carbohydrate approach.

Therefore, the “normal” levels in general medical guidelines reflect a sampling of the general population, which includes people with varying degrees of glucose control, rather than what might be achieved on a nutrient-dense or low-carb diet.

Do you have increased risk of retinopathy with an A1C of 5.6?
Yes, research suggests that people with an A1c in the upper end of the “normal” range, such as 5.6%, may still be at risk for developing retinopathy and other diabetes-related complications. While 5.6% is considered “normal” by standard medical guidelines (the threshold for prediabetes starts at 5.7%), studies have shown that complications like retinopathy can begin to occur at levels below the traditional diabetes diagnosis threshold.

Key Findings:

  1. Increased Risk Begins Around 5.5% A1c: Research, including data from the Diabetes Control and Complications Trial (DCCT), suggests that the risk of diabetic retinopathy starts to increase at A1c levels as low as 5.5%. This means that even people without diagnosed diabetes, but with A1c levels in the higher end of the “normal” range, can have a higher likelihood of developing complications.

  2. Retinopathy and A1c Levels: Some studies have indicated that the prevalence of retinopathy in individuals without diagnosed diabetes can begin at A1c levels between 5.5% and 6.0%, with the risk gradually increasing as A1c levels rise.

  3. Threshold for Ideal Safety: An A1c in the lower range, closer to 4.6-5.0%, is associated with very low risk for complications like retinopathy. The risk of complications increases as A1c moves closer to the upper end of the “normal” spectrum (5.5%-5.6%).

Why It Matters:

Even though an A1c of 5.6% falls within the “normal” range, it reflects an average blood sugar of around 114 mg/dL, which can lead to mild but persistent damage to the small blood vessels in the eyes, kidneys, and other organs over time. This damage may accumulate slowly, increasing the risk of complications, even in people who do not have full-blown diabetes.

Therefore, while an A1c of 5.6% is not immediately concerning under conventional standards, it’s clear that tighter glucose control—aiming for an A1c closer to 4.5-5.0%—provides better protection against complications like retinopathy.

Retinopathy becomes more likely as A1c levels increase, but at an A1c of 5.6%, the risk is relatively low compared to those with diabetes. However, there is still a measurable risk, as studies have shown that diabetic retinopathy can begin to occur in people with A1c levels in the upper end of the “normal” range, including at 5.6%.

Prevalence of Retinopathy at A1c of 5.6%

While specific data for the exact prevalence of retinopathy at an A1c of 5.6% are limited, here are some general insights:

  1. Low but Present Risk: Studies indicate that the risk of retinopathy begins to rise noticeably around an A1c of 5.5%. A large population study published in the New England Journal of Medicine found that retinopathy was rare at A1c levels below 5.5%, but the risk began to increase slightly between 5.5% and 6.0%, even in individuals without diagnosed diabetes.

  2. Risk Gradually Increases: In another study, the prevalence of retinopathy was found to be around 5% in individuals with an A1c between 5.5% and 6.0%. This is much lower than in individuals with diabetes (where the prevalence can be over 40%), but it shows that some risk exists even in this “normal” A1c range.

  3. Subclinical Retinopathy: At an A1c of 5.6%, retinopathy, if present, is more likely to be mild and not symptomatic. This stage is called subclinical retinopathy, where there may be small changes in the retina, but no vision problems yet.

Risk Context:

  • A1c of 5.6% corresponds to an average blood glucose of around 114 mg/dL, which is still higher than the 83-90 mg/dL range typically associated with the lowest risk for complications.
  • While the risk of retinopathy at this level is not as high as in people with diabetes, it’s important to note that the risk increases as A1c approaches the prediabetic range (5.7% and above).

Summary

At an A1c of 5.6%, the risk of retinopathy is low but not zero. Retinopathy is more common and severe in people with higher A1c levels, but evidence suggests that the risk of retinal changes starts to rise modestly even in the upper end of the “normal” A1c range, including 5.6%. This highlights the importance of maintaining tight glucose control, even for those without diagnosed diabetes, to minimize the long-term risk of complications.

Can an eye dr determine subclinical retinopathy?

Yes, an eye doctor can often detect subclinical retinopathy during a comprehensive eye exam, particularly through dilated retinal exams and advanced imaging techniques. Even though subclinical retinopathy may not cause noticeable symptoms, changes in the retina can be identified with specialized tools.

How Subclinical Retinopathy is Detected:

  1. Dilated Eye Exam: During a dilated eye exam, the eye doctor uses drops to dilate the pupils, allowing for a better view of the retina. This enables the doctor to examine the small blood vessels in the back of the eye for early signs of damage, such as:

    • Microaneurysms (tiny bulges in the blood vessels)
    • Hemorrhages (small areas of bleeding)
    • Retinal swelling or fluid leakage

  2. Fundus Photography: This is a high-resolution photo of the retina that can capture detailed images of the back of the eye. This allows the doctor to spot early changes in the blood vessels, even if they are too small to cause noticeable symptoms.

  3. Optical Coherence Tomography (OCT): OCT is an imaging test that creates cross-sectional images of the retina. It can detect subtle changes in the layers of the retina, such as swelling or thinning, which might indicate early stages of retinopathy. OCT is particularly useful for detecting diabetic macular edema, a complication of retinopathy that can occur even in the subclinical stage.

  4. Fluorescein Angiography: In some cases, an eye doctor may use fluorescein angiography, where a dye is injected into the bloodstream to highlight the retinal blood vessels. This helps detect abnormal blood flow or leakage that may not be visible through standard exams.

Can Subclinical Retinopathy Be Missed?

While an eye doctor using advanced diagnostic tools can typically detect early signs of subclinical retinopathy, very minor or subtle changes might not always be obvious during a basic exam. This is why individuals at higher risk, such as those with elevated A1c levels or diabetes, are often advised to have regular dilated retinal exams to catch any changes as early as possible.

Summary

An eye doctor, especially using tools like dilated exams, fundus photography, or OCT, can usually detect subclinical retinopathy. While it may not cause symptoms, the early detection of these subtle retinal changes can prompt more proactive management of blood sugar and eye health to prevent progression to more severe retinopathy.

Can it be reversed?
Yes, diabetic retinopathy, including its early subclinical stages, can often be slowed, halted, or even partially reversed with tighter blood sugar control. While full reversal of all retinal damage is not always possible, early interventions can significantly improve the condition and prevent it from progressing to more advanced stages.

How Tighter Blood Sugar Control Helps:

  1. Reducing Blood Vessel Damage: Elevated blood sugar damages the small blood vessels in the retina, causing them to leak, swell, or form new abnormal vessels (neovascularization). By maintaining tighter glucose control, these blood vessels are less likely to deteriorate further, which can stabilize or even reverse the damage.

  2. Lowering Risk of Progression: Studies have shown that intensive glucose control reduces the risk of progression from early-stage retinopathy to more severe forms. For example, the Diabetes Control and Complications Trial (DCCT) and its follow-up studies demonstrated that lowering A1c levels significantly reduced the risk of diabetic complications, including retinopathy.

    • In one study, participants with tighter glucose control (A1c below 7%) had about a 76% lower risk of developing retinopathy and a 54% lower risk of retinopathy progression.

  3. Possibility of Partial Reversal: While complete reversal of retinopathy is rare, especially in more advanced stages, improvements can often be seen with early intervention. In some cases of mild non-proliferative retinopathy (the early stage), retinal blood vessels may heal when blood glucose levels are kept consistently low. Microaneurysms (tiny bulges in blood vessels) can disappear, and retinal swelling may reduce.

  4. Improved Insulin Sensitivity: Better glucose control enhances insulin sensitivity, which can further stabilize blood sugar levels and reduce the risk of future retinal damage.

Other Factors That Can Help Reverse or Slow Retinopathy:

  • Blood Pressure Control: High blood pressure exacerbates damage to the retinal blood vessels. Keeping blood pressure within a healthy range can support the health of these vessels and prevent further damage.

  • Lipid Control: Elevated cholesterol or triglycerides can worsen retinopathy by contributing to blood vessel damage. Managing lipids, often through diet and medications, can complement tight glucose control.

  • Regular Eye Exams: Frequent monitoring by an eye specialist allows for early detection and timely intervention, such as laser therapy or anti-VEGF injections in more severe cases, to prevent vision loss.

Summary

Subclinical or early-stage diabetic retinopathy can be stabilized and potentially reversed with tight blood sugar control, typically by keeping A1c levels as low as possible, preferably under 6% or lower in some cases. The earlier tight control is implemented, the better the chances of halting or reversing the damage, especially if combined with other measures like blood pressure and lipid management.