What is fasting glucose?
Fasting glucose is a measure of how much sugar (glucose) is in your blood after you haven't eaten for at least 8–12 hours — usually first thing in the morning. It's one of the most common blood tests in the world and a basic check on how well your body manages blood sugar.
Think of it as a snapshot. It tells you what your blood sugar is doing right now, at rest, without food in the picture. It's useful, but it only shows one moment in time — which is why pairing it with HbA1c gives you a much more complete picture.
Why it matters for longevity
Blood sugar regulation is one of the cornerstones of healthy aging. When your fasting glucose is consistently elevated — even slightly — it means your body is struggling to clear sugar from the bloodstream efficiently. Over time, this leads to damage in your blood vessels, nerves, kidneys, and brain.
The tricky part is that fasting glucose is often the last thing to rise. Your body can keep fasting glucose looking "normal" for years while fasting insulin climbs higher and higher in the background. That's why checking both gives you much earlier warning.
What the numbers mean
The conventional medical ranges for fasting glucose are:
- Normal: 70–99 mg/dL
- Prediabetes: 100–125 mg/dL
- Diabetes: 126 mg/dL or higher
However, longevity-focused physicians consider the optimal range to be 72–85 mg/dL. A fasting glucose of 95 mg/dL is technically "normal," but it's already showing that your body's blood sugar control isn't as tight as it could be.
One thing to know about: the dawn phenomenon. Your body naturally releases in the early morning to wake you up, and this can push fasting glucose a bit higher than it would be at other times. If your morning reading seems unexpectedly high, this may be why. Testing at the same time each day helps you get consistent results.
What affects it
- Diet: Meals high in refined carbohydrates and added sugars cause larger blood sugar swings. Over time, this wears out your body's ability to regulate glucose effectively.
- Exercise: Physical activity helps your muscles pull glucose out of the blood without needing as much insulin. Regular movement — especially after meals — has a powerful effect.
- Sleep: Even one bad night of sleep can raise your fasting glucose the next morning. Poor sleep increases , making it harder for your body to process sugar.
- Stress: Chronic stress keeps cortisol elevated, which directly raises blood sugar levels.
- Women and PCOS: Women with polycystic ovary syndrome (PCOS) are more likely to have elevated fasting glucose and insulin resistance, even at a young age. If you have PCOS, tracking both fasting glucose and fasting insulin is especially important.
How to get tested
Fasting glucose is part of nearly every standard blood panel. You need to fast for at least 8 hours beforehand (water is fine). It's available through your regular doctor, urgent care clinics, and online lab services like Quest or Ulta Lab Tests. Most insurance covers it as part of routine blood work. For a fuller picture of your metabolic health, ask for HbA1c and fasting insulin at the same time.
How to improve it
- Walk after meals. A 10–15 minute walk after eating is one of the simplest, most effective ways to lower blood sugar spikes. Your muscles soak up glucose as you move, reducing how high your blood sugar climbs.
- Eat protein and fiber first. Starting your meal with vegetables, protein, or healthy fat — and eating carbs last — slows digestion and flattens your glucose curve.
- Build muscle. Muscle tissue is the biggest glucose sink in your body. The more muscle you have, the more efficiently your body handles sugar. Use our Macro Calculator to make sure you're eating enough protein to support muscle growth.
- Prioritize sleep. Consistent, quality sleep is one of the most underrated ways to improve blood sugar control. Aim for 7–9 hours per night.
- Cut back on liquid sugar. Sugary drinks, fruit juices, and sweetened coffees are some of the fastest ways to spike blood sugar. Swapping them for water, tea, or black coffee makes a big difference over time.