Why ‘Normal’ Blood Sugar Readings Don’t Always Mean You Feel Good After Eating

You’re not imagining it: The postmeal lull is real. Many people feel fatigued, foggy, or irritable after meals, even when lab tests show a normal A1C level.

A1C is an important indicator of whether medication and lifestyle changes are working, but “doesn’t reflect day-to-day changes in your eating habits, exercise, and stress,” says Allidina. That’s why these under-the-radar blood sugar fluctuations can affect how you feel, even if you may not know they’re happening.

If you’re taking steps to manage blood sugar levels, whether you have prediabetes, have type 2 diabetes, or are simply blood sugar aware, it helps to understand a few key things about how glucose is measured and what those numbers can — and can’t — tell you:

Fasting Glucose and Postmeal Glucose Spikes Are Not the Same

A1C Is an Average, Not a Day-to-Day Measurement

An A1C measurement estimates average blood sugar levels over the previous two to three months. That makes it useful for tracking long-term trends, but it does not capture short-term spikes and crashes, which can affect how you feel after meals.

Continuous Glucose Monitoring Can Help Reveal Patterns

“Wearing a [continuous glucose monitor] gives you incredible insight into how your body responds to not just food, but exercise, sleep, stress, and medications,” says Allidina.

Many Factors Influence Glucose Response

• Choice of food
• Exercise
• Certain medications, such as steroids
• Dehydration
• Hormonal changes
• Illness or infection
• Incorrect use of medications
• Injury or surgery
• Stress

What’s more, “The same food can cause very different blood sugar responses in different people,” says Allidina, due to these individual factors.

If you feel tired or irritable after a meal, one of the first things you can do is take a look at the foods and eating patterns that may be contributing to a postmeal glucose spike. As blood sugar comes back down from a high, some people feel a noticeable “crash.”

According to Allidina, a few foods and eating patterns commonly drive bigger blood sugar spikes:

• Low-Fiber, Carb-Heavy Meals Refined carbohydrates, such as crackers, pasta, sweets, and white bread, are low in fiber, so they’re digested fast. As a result, “Glucose hits the bloodstream very quickly,” says Allidina.
• Solo Carbohydrates Foods that contain fat, fiber, or protein — avocado, fish, nuts, olive oil, vegetables — act as “speed bumps” for your blood sugar, she says. That’s because these nutrients help slow digestion. “Pairing your carbs with these foods slows gastric emptying and blunts the glucose rise.”
• Liquid Carbohydrates Juice, smoothies, soda, and sweetened coffee drinks can be loaded with sugar (carbohydrates). And because you don’t need to chew them, they tend to raise blood sugar faster. “Chewing matters, and food structure matters. Liquid carbs hit the bloodstream very quickly,” says Allidina.
• Large, Carbohydrate-Heavy Portions Many carbohydrates have good nutritional value, including fruit, oats, and potatoes. But larger portions can still come with a heavy glucose load, which can lead to a higher blood sugar spike, followed by a more noticeable drop.

If you feel fatigued, have brain fog, become irritable or anxious, or have strong cravings within an hour or two of eating, you may be experiencing postmeal blood sugar swings, says Allidina.

The good news: Making small changes to what and how you eat can help support a steadier glucose response.

Use the Plate Method

• Fill half of the plate with nonstarchy veggies (such as asparagus, broccoli, or salad).
• Add protein (e.g., chicken, fish, or tofu) to 1/4 of the plate.
• Use 1/4 of the plate for carbohydrates (e.g., fruit or potatoes).
• Add small amounts of healthy fats (e.g., avocado or olive oil).

“This method naturally lowers the meal’s glycemic load and slows the rate at which glucose enters the bloodstream,” says Allidina.

Tackle Your Plate Strategically

See all those veggies? Dig into those and the protein at the beginning of the meal, and end with carbohydrates. Because fiber and protein blunt the absorption of glucose into your bloodstream, this small trick may help you avoid a spike.

“Same foods, different order, different response. If you get tired after meals, try this approach and see if that helps,” says Allidina.

Go for a Walk After You Eat

The result? You may feel better overall and more able to go back to your day.

• Feeling fatigued, foggy, or irritable after meals is common, and blood sugar swings may play a role, even if your A1C is normal.
• Standard lab tests, such as A1C and fasting glucose, don’t capture day-to-day or meal-by-meal spikes and crashes that can be triggered by habits such as eating large portions of refined carbs and drinking sugary beverages.
• To help prevent postmeal blood sugar slumps, build balanced meals with protein, fiber, and healthy fats; eat veggies and protein first; and take a short walk after meals.