What Should Your Blood Glucose Levels Be?

3 minute read

Your blood sugar levels are a measure of the amount of glucose in your blood at any given time. These levels naturally rise and fall throughout the day as your body breaks down the carbohydrates you eat into glucose, and then absorbs these glucose molecules into your bloodstream. But how much should your levels fluctuate? And when is it a cause for concern? We’ve put together a cheat sheet that walks you through ideal glucose levels for healthy individuals.

What are ideal fasting glucose levels?

Your fasting blood glucose level is a measure of the amount of glucose in your blood after a fasting period of 8 hours or more (i.e., your glucose levels upon waking). It’s an important number to monitor because your morning fasting glucose often reflects your body’s insulin sensitivity and how well your body is regulating blood sugar levels — which is why it’s often tested to check for conditions like prediabetes and diabetes [1].

Normal fasting blood glucose levels = 70 and 100 mg/dL (3.9 and 5.5 mmol/L)

If your fasting blood glucose levels are above 100 mg/dL (5.6 mmol/L), you may have insulin resistance [2].

What are normal glucose levels during the day?

In general, normal glucose levels in healthy, non-diabetic individuals stick to the following window before eating [3]:

Normal blood glucose levels before meals = 70 and 100 mg/dL (3.9 and 5.6 mmol/L)

As far as normal fasting glucose levels after eating (i.e., postprandial fasting glucose levels), here are the current guidelines for healthy, non-diabetic individuals [4]:

Normal levels two hours after eating = below 140 mg/dL (7.8 mmol/L)

While eating a meal that contains carbohydrates will always result in an increase in blood glucose levels, your body initiates a series of tightly controlled processes to bring those levels back down within a certain time frame.

In addition to keeping your postprandial glucose levels below 140 mg/dL (7.8 mmol/L), aim to keep your postprandial glucose rise <40 mg/dL (<2.5 mmol/L) — and ideally <30 mg/dL (<1.7 mmol/L).

Why? Data (here and here) shows that non-diabetic (and diabetic) individuals with higher postprandial glucose levels have an increased risk of cardiovascular disease and developing diabetes/IR compared to lower postprandial glucose levels [5, 6]. Limited research also suggests that healthy, non-diabetic individuals typically experience postprandial glucose levels <130 mg/dL (7.2 mmol/L) [7].

There are other studies that can provide us with a framework to understand what a postprandial glucose rise should generally look like in healthy people. In a 2009 study on 434 non-diabetic Chinese adults who wore a CGM, the reported mean fasting glucose levels were approximately 86 ± 7mg/dL, and average postprandial glucose levels 1-hour after eating were 121-123 mg/dL — which is an increase of less than 40 mg/dL [8]. Another 2010 study found that glucose levels in healthy individuals stayed between 71-120 mg/dL for 91% of the day [9]. A third study found that glucose levels only went above 140 mg/dL for 30 minutes per day in healthy people [10].

As you might expect, your diet plays a role in what your postprandial glucose levels look like. One study of 24 individuals ages 27.1 ± 3.6 years who wore a CGM for 2 days found that postprandial glucose concentrations ranged from 118.2 (± 13.4) mg/dL to 132.3 (± 16.7) mg/dL across breakfast, lunch, and dinner. But when participants ate meals high in fiber, protein, and fat, the increase was smaller (99.2 ± 10.5 mg/dL).

Current guidelines indicate that a postprandial blood glucose <140 mg/dL is considered normal for healthy individuals without diabetes, which is a reasonable absolute cutoff to go by. While there is currently no definitive, science-based range for a normal postprandial glucose rise, a good goal is to have a smoother curve, lower overall glucose peak, and fewer consecutive spikes. Veri users typically have a fasting glucose level between 70-90 mg/dL, so depending on your individual diet and activity level, it is reasonable to aim for a post-meal glucose increase of less than 40 mg/dL.

—

Dr. Vimal Ramjee, MD, FACC, CCMS

What are normal glucose levels at night?

Your glucose levels fluctuate during sleep, the time when your body makes essential repairs and releases glycogen (stored glucose) from the liver to provide itself with energy while you’re not eating. While these levels vary during different stages of sleep, your glucose levels will typically hover in the healthy fasting range (described earlier) at the beginning of the night and increase before waking as your body prepares to be active [12].

Normal glucose levels at the beginning of the night = 70 and 100 mg/dL (3.9 and 5.6 mmol/L)

Normal glucose levels before waking = 100+ mg/dL (5.6+ mmol/L)

What are high glucose levels?

In healthy, non-diabetic individuals, high glucose levels (hyperglycemia) are often the result of eating too many simple sugars without fiber, protein, or fat to slow the absorption of glucose into the bloodstream. But there are other non-diet factors as well, including dehydration, PCOS, insulin resistance, and genetics.

When glucose levels remain above 140 mg/dL or 7.8 mmol/L two hours after eating, you may have insulin resistance.

High glucose levels = above 180 mg/dL (10.0 mmol/L)

What are low glucose levels?

Low glucose levels (hypoglycemia) occur when your levels dip below the normal range. You may experience low glucose levels after eating too much sugar, which spikes your glucose levels (makes them higher than normal) and triggers your pancreas to release an excess of the hormone insulin to help bring those levels back down quickly (i.e., results in a “crash”) [13]. This is accompanied by classic hypoglycemic symptoms including shakiness, dizziness, fatigue, and sugar cravings (to bring your glucose levels back to normal).

Low glucose levels = below 70 mg/dL (3.9 mmol/L)

When should you be worried about your glucose levels?

Not all instances of high and low glucose levels are reasons for concern. Typically, you should pay attention to whether your glucose levels are chronically high or low — i.e., they remain higher or lower than normal after 8-10 hours of your last meal, repeatedly over time.

Other factors can lead to temporary spikes and dips in your blood glucose levels that are normal and healthy, including:

Drinking alcohol. Alcohol may temporarily lower your glucose levels (by increasing your insulin sensitivity), leading to a delayed spike. Drinking alcohol may also affect your sleep quality, which can reduce your insulin sensitivity the following day [4].
Compression hypoglycemia. If you wear a continuous glucose monitor (CGM), you may notice unusually low glucose levels at night. This is often the result of the sensor being compressed while sleeping on your side (which reduces blood flow to the area), leading to an inaccurate reading [14].
HIIT training. HIIT, or high-intensity interval training, and other challenging exercises can temporarily increase your glucose levels [15]. This happens because your liver releases more glucose into your bloodstream so your body has enough energy to complete the workout, and isn’t a cause for concern [16].

How do you manage your glucose levels?

You can manage your glucose levels by monitoring them with a CGM paired with an app like Veri. Veri tracks your glucose levels in real time and offers personalized insights into your metabolic health, allowing you to identify how your body responds to your diet and lifestyle. You can then use this information to build new habits that help you balance your levels, improve insulin sensitivity, and increase your healthspan.

Research suggests that the best way to manage your glucose levels is by focusing on Veri’s Four Pillars of Metabolic Health:

Diet. Eat metabolically healthy meals that are high in colorful vegetables, fiber, lean protein, and healthy fats — and low in sugar.
Exercise. Develop a consistent aerobic and resistance training routine to improve insulin sensitivity and body composition (which can help balance your glucose levels).
Sleep. Practice good sleep hygiene by sleeping around the same time every night, getting enough hours of sleep, and eliminating disruptions like light and noise.
Stress. Manage chronic stress, which can lead to elevated levels of the hormone cortisol — which can lead to insulin resistance and elevated glucose levels.

References:

Written by: James Han

Reviewed by: Emily Johnson, MSc RD

Table of Contents

What are ideal fasting glucose levels?
What are normal glucose levels during the day?
What are normal glucose levels at night?
What are high glucose levels?
What are low glucose levels?
When should you be worried about your glucose levels?
How do you manage your glucose levels?