Blood sugar levels are the amount of glucose (sugar) in your blood. For most adults, normal blood sugar levels are between 70–130 mg/dL (3.9–7.2 mmol/L) before meals, and less than 180 mg/dL (10 mmol/L) two hours after eating. Keeping your blood sugar steady helps prevent problems and makes you feel your best.
What Are Healthy Blood Sugar Levels?
Blood sugar levels change throughout the day, especially before and after meals. For people without diabetes, the body keeps these levels in a tight range. If you have diabetes or prediabetes, your blood sugar may rise higher, especially after eating. Knowing what is considered a good blood sugar level can help you stay healthy and avoid complications.
These are general targets. Your care team may set different goals for you, especially if you are older or have other health conditions (American Diabetes Association, NHS).
How to Check Your Blood Sugar Level
You can check your blood sugar at home using a finger-prick meter or a continuous glucose monitor (CGM). Many people with type 2 diabetes check their blood sugar at different times of day to see how food, activity, and stress affect their numbers. Here’s how to get started:
Wash your hands before checking to avoid false readings.
Follow your meter’s instructions and record your results.
Check at the same times each day for a clearer picture.
Talk to your care team about how often to check and what your targets should be.
Some people only need to check a few times a week, while others check more often. If you use insulin or certain diabetes medications, you may need to check more frequently.
What Blood Sugar Levels Are Dangerous?
Very high or very low blood sugar levels can be dangerous. If your blood sugar is below 70 mg/dL (3.9 mmol/L), this is called hypoglycemia and needs quick treatment. If your blood sugar is over 250 mg/dL (13.9 mmol/L), this is considered high (hyperglycemia), and over 400 mg/dL (22.2 mmol/L) can be an emergency. Symptoms of high blood sugar include thirst, tiredness, blurry vision, and needing to urinate more often. If you ever get a reading above 400 mg/dL (22.2 mmol/L) or below 54 mg/dL (3 mmol/L), contact your care team right away (CDC).
What Affects Blood Sugar Levels?
Many things can raise or lower your blood sugar, including:
Food: Carbohydrates (carbs) like bread, pasta, rice, fruit, and sweets raise blood sugar the most. The amount and type of carbs matter.
Physical activity: Exercise usually lowers blood sugar by helping your body use glucose for energy.
Stress and illness: Both can raise blood sugar, even if you don’t eat more.
Medications: Some medicines, especially for diabetes, affect blood sugar. Never change or skip your medication without talking to your care team.
Other factors, like not getting enough sleep or drinking alcohol, can also affect your blood sugar level.
Everyday Habits to Keep Blood Sugar Levels Steady
Small changes can make a big difference in keeping your blood sugar in a healthy range. Here are some practical tips:
Choose slow carbs: Pick whole grains (like brown rice or oats), beans, and vegetables over white bread, white rice, or sugary snacks. For example, one slice of whole grain bread has about 15g carbs, while a chocolate bar can have over 25g.
Watch your portions: Even healthy carbs can raise blood sugar if you eat too much. Use smaller plates or measure servings to help.
Eat regular meals: Skipping meals can make your blood sugar swing up and down. Try to eat at similar times each day.
Pair carbs with protein or healthy fats: This helps slow down how fast sugar enters your blood. For example, add eggs or nuts to your breakfast.
Stay active: A walk after meals or regular exercise can help lower blood sugar and keep it steady.
Drink water: Sugary drinks like soda or juice can spike your blood sugar. Water is always the best choice.
For more meal ideas, see our post Diabetic Diet for Beginners: 5 Easy, Healthy Swaps.
Blood Sugar Levels After Eating: What to Expect
It’s normal for blood sugar to rise after you eat, but it should return to your target range within 2–3 hours. For most adults with diabetes, the goal is to keep blood sugar under 180 mg/dL (10 mmol/L) two hours after eating. If you notice your blood sugar stays high after meals, try:
Eating smaller portions of starchy foods (like potatoes or pasta). A half-cup of cooked pasta is about 20g carbs.
Adding more non-starchy vegetables (like broccoli, carrots, or zucchini (courgette)).
Swapping white bread for whole grain, or rice for cauliflower rice.
Including lean protein, such as chicken, fish, tofu, or eggs.
If you need inspiration, check out our Ultimate Free 7-Day Diet Plan for Diabetic Patients.
What Is Bad for Blood Sugar Levels?
Certain foods and habits can make it harder to keep your blood sugar steady. Try to limit:
Sugary drinks: Soda, sweet tea, and fruit juice can cause quick spikes. A 12oz (355ml) can of soda has about 39g carbs.
Refined grains: White bread, pastries, and many breakfast cereals raise blood sugar faster than whole grains.
Large portions of starchy foods: Too much rice, pasta, or potatoes at once can send your blood sugar up.
Skipping meals: This can lead to low blood sugar followed by high spikes when you finally eat.
For more tips, see our post The Ultimate Guide to Food Swaps for Diabetics.
Frequently Asked Questions
What is the normal range for blood sugar levels?
The normal fasting blood sugar range for most adults is 70–99 mg/dL (3.9–5.5 mmol/L). Two hours after eating, it should be less than 140 mg/dL (7.8 mmol/L). For people with diabetes, your care team may set different goals based on your health needs (NIDDK).
Is a blood sugar level of 400 dangerous?
Yes, a blood sugar level of 400 mg/dL (22.2 mmol/L) is dangerous and can be a medical emergency. If you get this reading, contact your care team or seek medical help right away. High levels like this can lead to serious problems if not treated.
Can blood sugar levels affect blood pressure?
Yes, high blood sugar levels can make your blood pressure rise over time, especially if you have diabetes. Managing both your blood sugar and blood pressure is important to lower your risk of heart disease and stroke.
Can blood sugar levels affect eyesight?
Yes, both high and low blood sugar levels can affect your eyesight. High levels can cause blurry vision, and very high levels over time can damage the small blood vessels in your eyes. If you notice changes in your vision, talk to your care team.
Can blood sugar levels cause headaches?
Yes, both high and low blood sugar can cause headaches. If you have frequent headaches along with other symptoms like tiredness or blurry vision, check your blood sugar and talk to your care team.
What should blood sugar levels be for type 2 diabetes?
For most adults with type 2 diabetes, the goal is 80–130 mg/dL (4.4–7.2 mmol/L) before meals and less than 180 mg/dL (10 mmol/L) two hours after eating. Your care team may adjust these targets for you (American Diabetes Association).
What do blood sugar levels after eating tell you?
Checking your blood sugar after eating shows how your body handles food. If your numbers are high, you may need to adjust your portions, food choices, or timing of meals. Tracking these numbers helps you and your care team make better decisions.
Sources
CDC: Healthy Eating with Diabetes
Make it easier with GlucoForager
GlucoForager turns the food you already have into diabetes-friendly recipes, with carbs per serving, smart swaps and a glucose log that shows how meals affect you. Try it free or browse our free diabetes-friendly recipes.
This article is general information, not medical advice. Everyone's diabetes is different, so talk to your doctor, diabetes nurse or dietitian before making big changes to your diet or treatment.