Blood sugar level

Your body needs food to work.

Your body keeps the right amount of food in your blood. A part of your body helps do this. It makes a special helper to lower the food level. This helper tells your muscles to store the food for later.

If the food level gets too low, your body acts fast. It lets out more food to keep you going. This keeps your body steady and strong. It is a busy job for your body!

Your body needs sugar to work. This sugar is called glucose. It travels in your blood to give you power. Your brain uses much of this sugar to think.

Your body works hard to keep glucose at a steady level. This is called homeostasis. A part of your body called the pancreas helps. It makes a hormone called insulin. A hormone is a special helper in your blood. Insulin lowers your blood sugar. It tells your muscles to store extra sugar as glycogen. Glycogen is a way to save sugar for later.

If your sugar gets too low, your body acts fast. It lets out sugar from your liver. This keeps you steady. If your sugar stays too high, it can cause health problems. This is called hyperglycemia. If your sugar is too low, it is called hypoglycemia. People with diabetes may have these issues. Doctors can use a monitor to check your levels. This helps keep your body healthy and strong.

Your body needs a steady supply of energy to work well. This energy comes from a sugar called glucose. Glucose travels through your bloodstream to reach different parts of your body. It is very important for your brain to have enough glucose. In fact, a resting brain uses about 60% of the glucose in your blood. Even though it is vital, the amount of sugar in your blood is very small. For a person weighing 70 kg, there are only about four grams of glucose in the blood plasma at any time.

Your body uses a clever way to keep these levels steady. This process is called homeostasis. Your pancreas helps by making a hormone called insulin. A hormone is a special messenger in your blood. When your blood sugar rises after a meal, insulin tells your cells to take in the glucose. It also tells your muscles and liver to store extra sugar as glycogen. If your sugar gets too low, your body releases that stored glycogen back into the blood. This cycle of using insulin and glucagon keeps everything balanced.

Doctors use different names for blood sugar levels that are not normal. When levels stay too high, it is called hyperglycemia. When they drop too low, it is called hypoglycemia. If someone has diabetes, their body struggles to regulate these levels. This can lead to many health problems over a long time. For example, very high sugar can lead to damage in the eyes, kidneys, or nerves. On the other hand, very low sugar can make a person feel shaky or weak. It can even cause someone to lose consciousness if it is not fixed quickly.

There are different ways to measure how much sugar is in your blood. In the United States, doctors often use milligrams per decilitre, or mg/dL. In the United Kingdom and many other countries, they use millimoles per litre, or mmol/L. A normal fasting blood sugar for a person without diabetes is between 3.9 and 5.5 mmol/L. This is the same as 70 to 100 mg/dL. For someone with diabetes, the target fasting range is slightly higher, between 3.9 and 7.2 mmol/L. These numbers help doctors make sure the body is staying in a safe range.

Many different living things have their own ways of managing sugar. Most animals have different ranges than humans. For example, a dog usually has a range between 62 and 108 mg/dL. A cat's range is between 61 and 124 mg/dL. Even large animals like the white rhinoceros have different levels. In the past, doctors had to take blood samples to check these levels. Now, since 2015, some people can use a continuous glucose monitor. This device uses an electrode placed under the skin to check sugar levels constantly.

Blood sugar level, also known as glycemia, is the measure of glucose concentration in the blood. Glucose is a simple sugar that serves as a primary energy source for the body. Maintaining steady levels is vital for metabolic homeostasis, which is the body's way of keeping internal conditions stable. For a 70 kg human, only about four grams of dissolved glucose are maintained in the blood plasma at any time. This is a very small amount, roughly equivalent to one teaspoon of sugar in a person with five liters of blood.

The body regulates this process through a complex system of hormones and feedback loops. The pancreas contains bundles of endocrine tissue called islets, which produce different types of cells. Beta cells secrete insulin, which is an anabolic hormone that lowers blood glucose. When insulin is released, it signals cells to take up glucose for energy or storage. It also instructs the muscles and liver to store excess glucose as glycogen. Conversely, alpha cells secrete glucagon, a catabolic hormone that increases blood glucose. Glucagon triggers the release of glucose from glycogen stores when levels drop too low.

This regulation works through a process called negative feedback. In this cycle, the end product of a reaction stimulates the beginning of another to restore balance. When blood glucose rises, insulin is secreted to lower the concentration. As the level drops, the lower concentration triggers the secretion of glucagon. Other hormones like epinephrine and cortisol also play roles in this system. Epinephrine prepares the body for a "fight or flight" response, while cortisol provides fuel during heavy stress. Even skeletal muscle activity can influence glucose levels through an enzyme called AMPK.

There are two main abnormal states regarding blood sugar: hyperglycemia and hypoglycemia. Hyperglycemia occurs when blood glucose levels are persistently high. This is the primary characteristic of diabetes mellitus, a disease where the body fails to regulate sugar properly. Long-term hyperglycemia can lead to glucose toxicity, causing damage to the eyes, kidneys, nerves, and heart. On the other hand, hypoglycemia refers to blood sugar levels that are too low. This is often seen in people with type 1 diabetes or liver disease. Severe hypoglycemia can cause shakiness, sweating, confusion, or even loss of consciousness.

Medical professionals use different units to measure these levels depending on the region. In the United States, Germany, and Japan, mass concentration is measured in mg/dL (milligrams per decilitre). In the United Kingdom, Australia, and Canada, molar concentration is measured in mmol/L (millimoles per litre). For a non-diabetic person, a normal fasting blood glucose range is 3.9–5.5 mmol/L, or 70–100 mg/dL. The American Diabetes Association sets a fasting target for diabetics between 3.9–7.2 mmol/L. For those with diabetes, glucose levels should stay below 10 mmol/L (180 mg/dL) two hours after a meal.

Different species have evolved different blood sugar ranges to suit their biology. Most domestic ruminants, such as cows and sheep, have lower ranges than monogastric mammals. For example, a cow's serum glucose range is 42 to 75 mg/dL, while a dog's range is 62 to 108 mg/dL. Even marine animals have specific levels, such as beluga whales, which have an estimated range of 94 to 115 mg/dL. Wild animals like the white rhinoceros show a 95 percent range of 28 to 140 mg/dL. These variations show how different life forms manage energy through their bloodstreams.

Understanding blood sugar is essential because certain organs require a constant supply of glucose. The human brain is a major consumer, using approximately 60% of blood glucose in fasting, sedentary individuals. Because the brain is so metabolically active, low glucose levels can be extremely dangerous. While hyperglycemia is a serious long-term risk, hypoglycemia can cause immediate, life-threatening consequences. This is why doctors monitor glucose levels using blood samples or continuous glucose monitors. These monitors use an electrode placed under the skin to track levels constantly.