How to know if your blood sugar levels are healthy

• It's important to know what a normal blood sugar is if you have diabetes, or if you may be at risk. 

• For diabetics, normal blood sugar levels are considered between 80 to 130 mg/dL after fasting, and less than 180 mg/dL one to two hours after eating. 

• For those without diabetes, normal blood sugar levels are considered between 70 to 99 mg/dL after fasting, and less than 140 after eating. 

• This article was medically reviewed by Jason R. McKnight, MD, MS, a family medicine physician and clinical assistant professor at Texas A&M College of Medicine. 

• Visit the Insider's Health Reference library for more advice.

If you have diabetes, daily management of your blood sugar levels is important to feeling your best and preventing long-term health complications. 

Blood sugar can also be an important measurement to determine your risk for diabetes. For example, those with prediabetes will have their blood sugar tested at least annually, as abnormal blood sugar levels can indicate you may be likely to develop type 2 diabetes. 

Here's what you need to know about how blood sugar is measured, what's considered normal, and how to regulate blood sugar if it's too high or low. 

                                                    What is blood sugar? 

Blood sugar, or blood glucose, is a measurement of the amount of glucose in your blood. 

When you eat carbohydrates, your body breaks down those carbs into glucose. This becomes your body's main source of energy, and fuels the vital functions in your brain, heart, liver, and muscles, says Nestoras Mathioudakis, MD, a diabetes expert at Johns Hopkins Medicine. 

For people without diabetes, the pancreas releases insulin to help your cells absorb glucose and fuel your body. But for people with diabetes, the body does not produce insulin or it doesn't work properly, and as a result, blood sugar levels must be carefully regulated to prevent health complications. 

                             How to measure blood sugar levels  

There are two main ways to check your blood sugar levels: 

1. Blood glucose test. There are many at-home devices — such as finger-prick monitoring kits or continuous glucose monitors — that you can use to measure blood sugar on your own.  
2. An A1C test. A1C is a blood test, conducted by your doctor, that describes your average blood sugar levels for the past three months. 

Type 1 diabetics, along with some type 2 diabetics, who require insulin medication, must check their blood sugar at least four times per day, says Mathioudakis. Typically, this should be done before a meal, one to two hours after a meal, and at bedtime. 

The timing of these measurements can help determine how much insulin to use. For example, it can be important to use more insulin after a high-sugar meal or to avoid falling into hypoglycemia while you're sleeping. 

To check your blood sugar at home, you should use blood glucose tests, such as a glucose meter or continuous glucose monitor (CGM). Both devices measure blood sugar with the unit mg/dL, which means a milligram of sugar per deciliter of blood. 

If you don't have diabetes, but you may be at risk, your doctor might have you take an A1C test during a yearly check-up. This test report results as a percentage; the higher the percentage, the higher your blood sugar has been in the past three months. Those with diabetes should get an A1C test at least twice a year — and sometimes every three months. 

                                       What's normal? 

The following chart depicts normal blood sugar measurements, depending on which test you use and when you take it. 

Overall, what is considered a normal blood sugar level can look different depending on someone's age, weight, gender, and other factors. 

For example, a 2017 study published in the journal Physiology & Behavior suggests that women could have lower fasting blood glucose levels and be more insulin resistant due to lower muscle mass compared to men. However, the same study finds that pre-diabetic symptoms like impaired fasting glucose are more common among men. Normal blood sugar levels also increase as you age.

So, talk with your doctor about what normal blood sugar is for you in order to best manage your health. 

                       How to regulate your blood sugar levels 

Most of the time, you'll be able to regulate your blood sugar on your own if it's too high or low. 

If your levels are too high — over 140 mg/dL before a meal or 180 mg/dL after a meal — you may be experiencing hyperglycemia. Symptoms can include: 

Headache 

Irritability

Fatigue 

Frequent urination

Excess thirst

To lower blood sugar, you'd want to use more insulin medication to help your cells absorb glucose. 

On the other hand, hypoglycemia is when your blood sugar is too low, typically under 70 mg/dL. Common signs may include: 

Hunger

Nausea

Confusion

Feeling shaky or sweaty

Blurred vision

If you need to raise your blood sugar, you should eat a glucose tablet or drink something sugary, such as fruit juice. 

Mathioudakis says that those with a family history of diabetes — and who show high fasting glucose — should talk with their doctor about how to regulate blood sugar levels. And if your blood sugar spikes too high, such as 200 mg/dL or more, you should seek immediate medical attention