Blood sugar levels need to be in a normal range for you to be healthy. At least some blood sugar is necessary for your muscle, liver, and some other cells to use as fuel so they can function.
Abnormal – too much or too little sugar, though, is dangerous. Too little blood sugar, or hypoglycemia, can make you weak or even lead to loss of consciousness. On the other hand, hyperglycemia, or too much blood sugar in your blood, can also become an emergency or lead to diabetes complications.  A blood sugar chart can help you remember which levels you should have, especially if you're not diabetic yet and want to keep it at bay.
Normal and Abnormal Blood Sugar Levels and What They Mean
The ranges of normal levels of blood sugar depend on factors such as what time of day it is and when you last ate. Safe levels of blood sugar are high enough to supply your organs with the sugar they need, but low enough to prevent symptoms of abnormal blood sugar. Dangerous levels of blood sugar are outside of this range.
The target levels can also vary if you have diabetes. For example, if you are diabetic and are monitoring your blood sugar, you might get a reading of 65 mg/dl. That is considered to be mild hypoglycemia, and you would be wise to eat 15 grams of fast-acting carbohydrates and retest your blood sugar in 15 minutes.
If you were not diabetic, you probably would not know that your sugar was low because you would not test and because you would not have symptoms, and you would not act. That is fine because your body is capable, under normal circumstances, of raising your blood sugar to healthy, normal levels when needed, even if you have not eaten. That's the primary difference between someone who has diabetes and someone who doesn't.
Blood Sugar Levels in the Morning
The best time to check blood sugar levels in the morning is right when you wake up and before you eat anything. This gives you a glimpse of what may be happening overnight, and it gives you a baseline for the day.
The dawn effect can often lead to a high morning measurement in diabetes. This is your body's tendency to get ready for the day by raising blood sugar by increasing levels of counter-regulatory hormones – the ones that counteract insulin. With diabetes, you do not have the capacity to counterbalance this rise in blood sugar, so levels can be dangerously high. 
After eating, your blood sugar levels rise. They rise more when you eat more carbohydrates, when you do not eat fiber, fat, or protein with your carbs, and when you eat certain types of carbohydrates, such as refined sugars and starches.
You might want to measure your blood sugar before meals to get a baseline, and then two hours after your meal. Your doctor might also suggest measuring blood sugar before bed to be sure you have been eating well throughout the day and can go to sleep with peace of mind. These are target normal values. 
Goals for Healthy Adults
Goals with Diabetes
Before lunch, dinner, or a snack
Less than 110 mg/dl
2 hours after you eat
Less than 140 mg/dl
Less than 180 mg/dl
Less than 120 mg/dl
Blood Sugar Levels during Pregnancy
Gestational diabetes is high blood sugar that occurs during pregnancy if you were not diabetic before getting pregnant.  Healthy, normal blood sugar during pregnancy can help lower your risk of developing type 2 diabetes later. It can also lower the risk of your baby being born prematurely, at a high birth weight, and having respiratory problems.
Blood sugar and insulin levels during the first trimester of pregnancy tend to be lower than usual, but they rise during the late second and early third trimesters. You can be diagnosed with an oral sugar tolerance test (OGTT). 
These are the steps for the 2-step strategy.
Drink a solution with 50 grams (200 calories) of sugar – about the amount in 1 16-oz. bottle of a soft drink.
Get your blood drawn after 1 hour. IF the value is high, retest‚
Drink a solution with 100 grams (400 calories) of sugar – about the amount in 12(!) peanut butter cups.
Get your blood drawn immediately and after 1, 2, and 3 hours.
Or, your doctor might use the 1-step strategy with a 2-hour OGTT.
Drink a solution with 75 grams of sugar (300 calories – about the amount in 2 cans of soda).
Get your blood drawn immediately and after 1 and 2 hours.
These are some values to know related to gestational diabetes and healthy, normal blood sugar in pregnancy. 
Time or Situation
Blood Sugar Values
Diagnosis – 1-hour OGTT
Any of the following are indicative of gestational diabetes.
Fasting: 92 mg/dl 1 hour: at least 180 mg/dl 2 hours: at least 153 mg/dl
Diagnosis – 2-hour OGTT
Getting 2 or more of the values shown is indicative of gestational diabetes.
Baseline: at least 95 mg/dl 1 hour: at least 180 mg/dl 2 hours: at least 155 mg/dl 3 hours: at least 140 mg/dl
(Alternative Method) Baseline: at least 105 mg/dl 1 hour: at least 190 mg/dl 2 hours: at least 165 mg/dl 3 hours: at least 145 mg/dl
Hemoglobin is the oxygen-carrying protein in your red blood cells, but it is highly relevant to blood sugar levels. Sugar in your blood attaches to hemoglobin, creating what is called glycated hemoglobin, or A1C. High blood sugar levels lead to more hemoglobin being glycated.
A blood sugar chart showing goal values can help you quickly gauge how you are doing with your monitoring. This chart shows what to aim for throughout the day if you have diabetes or not. 
Time and Situation
Goal for Non-Diabetics
Goal for Diabetics
First thing in the morning (fasting before breakfast)
< 100 mg/dl
70 – 130 mg/dl
Before lunch, dinner, and snacks
< 110 mg/dl
70 – 130 mg/dl
Two hours after starting to eat a meal or snack
< 140 mg/dl
< 180 mg/dl
Before going to bed
< 120 mg/dl
90- 150 mg/dl
You can also click here for a printable blood sugar chart showing target values at different times of the day for diabetics and non-diabetics.
Normal Blood Sugar Level Chart by Age
Blood sugar levels tend to rise with age due to an increase in insulin resistance and decrease in insulin sensitivity. In one study, each extra decade of age was linked to a 2.7 mg/dl increase in fasting sugar, and a 4.5 mg/dl increase in 2-hour post-prandial (post-meal) sugar levels. 
How to Reduce Blood Sugar
You can take steps to reduce blood sugar as soon as you find out that it is high. This is how to reduce blood sugar if you have a single high reading that may be dangerous:
Ask your doctor what to do if you missed a dose of insulin or another diabetes medication.
Ask your doctor if your medication type(s) and dose(s) are still appropriate for you.
Drink water to dilute the sugar.
Exercise (if safe) for 15 minutes.
Eat a small protein snack, such as a hard-boiled egg, 1/2 ounce of peanuts or pistachios or other nuts, 1/2 cup of beans, or 1/2 cup of plain yogurt or cottage cheese.
Exercise regularly, assuming your doctor approves it.
Lose weight if you are overweight or obese.
Eat a higher proportion of vegetables, whole grains, lean proteins, healthy fats, and fruit.
Limit sugary foods and beverages, fried foods, refined starches, and processed and fatty red meats.
Blood Sugar Level Calculator
If you have your blood sugar levels tested, then what? A blood sugar level calculator can help you put the results into terms you can understand. For example, it can convert mg/dl into mmol, or mmol into mg/dl, depending on which value your test results state for sugar levels. A calculator can also change A1C into EAG, or estimated average sugar.
Fasting Blood Sugar Level Test Preparation
What should you do if your doctor orders a fasting blood sugar test? The preparation is the same as when you take a fasting test for cholesterol. First, be sure to find out if you need to schedule an appointment for your test (some people need to; others have providers that do not require an appointment for blood tests). Ask your doctor what time is best to take it.
Schedule your test if necessary.
Ask your doctor if you need to change any of the medications you take on the morning of the test.
If you normally drink coffee or have caffeine, ask your doctor if that is okay. It may not be, since it affects blood sugar levels.
Fast for at least 8 hours before your test. Usually, an overnight fast is most convenient.
You can drink water.
How to Check Blood Sugar Levels of Urine at Home
A home urine test can show if you are excreting sugar in your urine. That only happens when blood sugar levels are high, and not if your values are within a healthy range. The urine test uses a test strip and is simple to do, but is not very precise.
Blood Sugar Test Machine
Blood tests are more common urine tests for measuring blood sugar. They are precise, quick, and not overly painful. A blood sugar testing machine is also called a glucometer. It is not being overly dramatic to say that a good home glucometer can be life-saving if you have diabetes, since monitoring your blood sugar is one of the top strategies for controlling it.
A good home glucometer:
Is simple, fast, and accurate.
Is easy to set up and use.
Pairs with a diabetes smartphone app so you can see your values instantly, track them over time, and get coaching and feedback.
Lark Diabetes Coach comes with a complete home glucometer kit that is shipped to you and is easy to set up. The Lark app walks you through setup and reminds you when to take your blood sugar.
Lark helps you eat better, move more, stress less, and improve your overall wellness. Lark’s digital coach is available 24/7 on your smartphone to give you personalized tips, recommendations, and motivation to lose weight and prevent chronic conditions like diabetes.