blood sugar level blood sugar level glycaemia, also known as blood sugar level, blood sugar concentration, or blood glucose level is the measure of glucose concentrated in the blood. the body tightly regulates blood glucose levels as a part of metabolic homeostasis. the fluctuation of blood sugar (red) and the sugar-lowering hormone insulin (blue) in humans during the course of a day with three meals. one of the effects of a sugar-rich vs a starch-rich meal is highlighted. for a 70 kg (154 lb) human, approximately 4 grams of dissolved glucose is maintained in the blood plasma at all times. glucose is also stored in skeletal muscle and liver cells in the form of glycogen; in fasting individuals, blood glucose is maintained at a constant level by using glycogen stores in the liver and skeletal muscle. glucose can be transported from the intestines or liver to other tissues in the body via the bloodstream. cellular glucose uptake is primarily regulated by insulin, a hormone produced in the pancreas. in humans, properly maintained glucose levels are necessary for normal function in a number of tissues, including the human brain, which consumes approximately 60% of blood glucose in fasting, sedentary individuals. a persistent elevation in blood glucose leads to glucose toxicity, which contributes to cell dysfunction and the pathology grouped together as complications of diabetes. glucose levels are usually lowest in the morning, before the first meal of the day, and rise after meals for an hour or two by a few millimoles. abnormal persistently high glycemia is referred to as hyperglycemia; low levels are referred to as hypoglycemia. diabetes mellitus is characterized by persistent hyperglycemia from a variety of causes, and it is the most prominent disease related to the failure of blood sugar regulation. there are different methods of testing and measuring blood sugar levels. drinking alcohol causes an initial surge in blood sugar and later tends to cause levels to fall. also, certain drugs can increase or decrease glucose levels. units there are two ways of measuring blood glucose levels: in the united kingdom and commonwealth countries (australia, canada, india, etc.) and ex-ussr countries molar concentration, measured in mmol/l (millimoles per litre, or millimolar, abbreviated mm). in the united states, germany, japan and many other countries mass concentration is measured in mg/dl (milligrams per decilitre). since the molecular weight of glucose c6h12o6 is 180, the difference between the two units is a factor of 18, so 1 mmol/l of glucose is equivalent to 18 mg/dl. normal value range humans normal value ranges may vary slightly between laboratories. glucose homeostasis, when operating normally, restores the blood sugar level to a narrow range of about 4.4 to 6.1 mmol/l (79 to 110 mg/dl) (as measured by a fasting blood glucose test). normal blood glucose level (tested while fasting) for non-diabetics is between 3.9 and 7.1 mmol/l (70 and 130 mg/dl). the global mean fasting plasma blood glucose level in humans is about 5.5 mmol/l (100 mg/dl); however, this level fluctuates throughout the day. blood sugar levels for those without diabetes and who are not fasting should be below 6.9 mmol/l (125 mg/dl). the blood glucose target range for diabetics, according to the american diabetes association, should be 5.0–7.2 mmol/l (90–130 mg/dl) before meals and less than 10 mmol/l (180 mg/dl) two hours after meals (as measured by a blood glucose monitor). despite widely variable intervals between meals or the occasional consumption of meals with a substantial carbohydrate load, human blood glucose levels tend to remain within the normal range. however, shortly after eating, the blood glucose level may rise, in non-diabetics, temporarily up to 7.8 mmol/l (140 mg/dl) or slightly more. for people with diabetes maintaining "tight diabetes control", the american diabetes association recommends a post-meal glucose level of less than 10 mmol/l (180 mg/dl) and a fasting plasma glucose of 3.9 to 7.2 mmol/l (70–130 mg/dl). the actual amount of glucose in the blood and body fluids is very small. in a healthy adult male of 75 kg (165 lb) with a blood volume of 5 l, a blood glucose level of 5.5 mmol/l (100 mg/dl) amounts to 5 g, equivalent to about a teaspoonful of sugar. part of the reason why this amount is so small is that, to maintain an influx of glucose into cells, enzymes modify glucose by adding phosphate or other groups to it. other animals in general, ranges of blood sugar in common domestic ruminants are lower than in many monogastric mammals. however this generalization does not extend to wild ruminants or camelids. for serum glucose in mg/dl, reference ranges of 42 to 75 for cows, 44 to 81 for sheep, and 48 to 76 for goats, but 61 to 124 for cats; 62 to 108 for dogs, 62 to 114 for horses, 66 to 116 for pigs, 75 to 155 for rabbits, and 90 to 140 for llamas have been reported. a 90 percent reference interval for serum glucose of 26 to 181 mg/dl has been reported for captured mountain goats (oreamnos americanus), where no effects of the pursuit and capture on measured levels were evident. for beluga whales, the 25–75 percent range for serum glucose has been estimated to be 94 to 115 mg/dl. for the white rhinoceros, one study has indicated that the 95 percent range is 28 to 140 mg/dl. for harp seals, a serum glucose range of 4.9 to 12.1 mmol/l has been reported; for hooded seals, a range of 7.5 to 15.7 mmol/l has been reported. regulation main article: blood sugar regulation the body's homeostatic mechanism keeps blood glucose levels within a narrow range. it is composed of several interacting systems, of which hormone regulation is the most important. there are two types of mutually antagonistic metabolic hormones affecting blood glucose levels: catabolic hormones (such as glucagon, cortisol and catecholamines) which increase blood glucose; and one anabolic hormone (insulin), which decreases blood glucose. these hormones are secreted from pancreatic islets (bundles of endocrine tissues), of which there are four types: alpha (a) cells, beta (b) cells, delta (d) cells and f cells. glucagon is secreted from alpha cells, while insulin is secreted by beta cells. together they regulate the blood-glucose levels through negative feedback, a process where the end product of one reaction stimulates the beginning of another reaction. in blood-glucose levels, insulin lowers the concentration of glucose in the blood. the lower blood-glucose level (a product of the insulin secretion) triggers glucagon to be secreted, and repeats the cycle. in order for blood glucose to be kept stable, modifications to insulin, glucagon, epinephrine and cortisol are made. each of these hormones has a different responsibility to keep blood glucose regulated; when blood sugar is too high, insulin tells muscles to take up excess glucose for storage. glucagon responds to too low of a blood glucose level; it informs the tissue to produce more glucose. epinephrine prepares the muscles and respiratory system for activity in the case of a "fight and flight" response. lastly, cortisol supplies the body with fuel in times of heavy stress. abnormalities