Lab result explainedMetabolic panelLast updated November 10, 2026

Lactic acid (lactate) blood test: normal range, what high lactate means and lactic acidosis levels

Lactic acid (lactate) (Lactate) · Ordered alone or with a blood gas; sepsis and critical-care panels · reported in mmol/L on most US reports (some use mg/dL; 1 mmol/L = 9 mg/dL)

Lactic acid, measured in blood as lactate, is produced when cells make energy without enough oxygen or when the usual route of sugar metabolism is blocked. Everyone makes some, and the liver and kidneys clear it, so a healthy resting level is about 0.5 to 2.2 mmol/L (4.5 to 20 mg/dL). The lactic acid blood test is one of the most important tests in emergency and intensive care medicine, because a rising lactate is an early sign that tissues are not getting the oxygen or blood flow they need, often before blood pressure falls.

A lactate between 2 and 4 mmol/L is called hyperlactatemia; above 4 mmol/L, especially with a low blood pH, it is lactic acidosis. In sepsis, a lactate of 2 or more is part of the definition of septic shock and a level of 4 or more triggers urgent fluid resuscitation. Mortality rises steeply with the number: in emergency department patients with infection, death rates of roughly 5 percent with lactate under 2.5, 9 percent between 2.5 and 4, and 28 percent above 4 mmol/L have been reported.

Not every high lactate means a crisis. Hard exercise can push it above 15 mmol/L for an hour, a seizure raises it transiently, and a tight tourniquet or a delayed sample adds to the reading. Medicines (metformin, some HIV drugs, inhaled albuterol), liver disease, alcohol, thiamine deficiency and some cancers raise lactate without any lack of oxygen. The number is read with how you look, your blood pressure, your pH and bicarbonate, and whether it is falling on a repeat test an hour or two later.

Lactate at a glance

What it is: the end product of anaerobic metabolism; rises when tissues lack oxygen or blood flow, or when the liver cannot clear it.
Normal venous lactate: 0.5–2.2 mmol/L (4.5–20 mg/dL); arterial slightly lower at 0.5–1.6. Labs differ slightly.
2–4 mmol/L: hyperlactatemia; over 4 mmol/L with a low pH: lactic acidosis, a medical emergency until the cause is found.
Sepsis thresholds: lactate ≥2 mmol/L with low blood pressure defines septic shock; ≥4 triggers 30 mL/kg of IV fluid; a fall of at least 10–20 percent within 2 to 6 hours shows treatment is working.
Common non-emergency causes: hard exercise, seizures, tourniquet or delayed sample, metformin, alcohol, liver disease, albuterol, thiamine deficiency.
Low lactate is not a concern. Next step for a high value: repeat on a properly collected sample and treat the cause (fluids, oxygen, antibiotics, stopping a culprit drug).

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What Lactate measures

Cells break glucose down to pyruvate. With enough oxygen, pyruvate enters the mitochondria and is burned for energy; without it, lactate dehydrogenase converts pyruvate to lactate so that glycolysis can keep going. The lactate then travels to the liver, where most of it is turned back into glucose (the Cori cycle), and to the kidneys, which clear and use the rest. A blood lactate therefore rises when production outstrips clearance: when tissues are starved of oxygen or blood flow (type A lactic acidosis) or when metabolism or clearance is disrupted without hypoxia (type B).

The test is run on venous or arterial blood, often as part of a blood gas, and reported in mmol/L in most US hospitals (1 mmol/L equals 9 mg/dL). Venous and arterial values are close enough that a venous sample is used for screening. Point-of-care analyzers give a result within minutes, which is why lactate is repeated every 1 to 2 hours in sepsis and shock to see whether it is clearing.

Collection matters. Red cells keep making lactate in the tube, so blood should go into a gray-top (fluoride-oxalate) tube or be placed on ice and analyzed within about 15 minutes; left at room temperature in a plain tube, lactate climbs by several tenths of a mmol/L every 30 minutes. A prolonged tourniquet, fist clenching, or a struggling, hyperventilating or recently exercised patient can add 0.5 to 2 mmol/L. A mildly raised value from a difficult draw is repeated before it is acted on.

Normal range for Lactate

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

Group	Typical range (mmol/L on most US reports (some use mg/dL; 1 mmol/L = 9 mg/dL))	Notes
Normal, venous blood	0.5–2.2 mmol/L (4.5–20 mg/dL)	Arterial values run slightly lower, about 0.5–1.6 mmol/L. Labs differ slightly; use the range on your report.
Mild hyperlactatemia	2–4 mmol/L	Early tissue hypoperfusion, dehydration, infection, seizure, exercise, metformin, alcohol, albuterol, liver disease, or a poorly collected sample. Needs a cause and a repeat.
Lactic acidosis	Above 4 mmol/L, usually with pH below 7.35 and low bicarbonate	Shock, sepsis, severe hypoxia, bowel or limb ischemia, cardiac arrest, poisoning, metformin toxicity. Treated as an emergency.
Septic shock definition (Sepsis-3)	Lactate above 2 mmol/L despite fluids, with a vasopressor needed to keep blood pressure up	Hospital mortality in this group is around 40 percent.
Sepsis resuscitation trigger	4 mmol/L or more	Surviving Sepsis Campaign: give 30 mL/kg of intravenous crystalloid within 3 hours and remeasure lactate within 2 to 4 hours.
Severe	Above 8–10 mmol/L	Very high mortality unless the cause is reversed quickly; exceptions are transient rises after a seizure or maximal exercise, which fall within 1 to 2 hours.
After maximal exercise	Transiently 10–25 mmol/L	Sprinting or an all-out effort can briefly reach these levels in healthy people; back to baseline within 1 to 2 hours of rest.
Newborns	Up to about 3 mmol/L in the first hours	Falls to adult values over the first day or two; persistent elevation prompts evaluation for infection, heart disease or metabolic disorders.
Cerebrospinal fluid	Below about 2.5–3.5 mmol/L	A CSF lactate above this favors bacterial over viral meningitis when the two are hard to tell apart.

High lactic acid (hyperlactatemia and lactic acidosis)

A high lactate means your cells are producing lactate faster than your liver and kidneys can clear it. In an emergency setting the first assumption is that tissues are not getting enough oxygen or blood flow (type A): sepsis, dehydration, bleeding, heart failure, a heart attack, a blocked artery to the bowel or a limb, severe asthma or pneumonia, cardiac arrest, carbon monoxide or cyanide poisoning, or a prolonged seizure. In these situations the lactate is a measure of how severe the problem is and whether treatment is working, and it is repeated every one to two hours until it falls.

A high lactate in someone whose circulation and oxygen levels are fine points to a type B cause: the liver's clearance is impaired (cirrhosis, liver failure, alcohol), a medicine is interfering with mitochondria (metformin when kidneys fail, the older HIV nucleoside drugs, linezolid, propofol infusions, high-dose albuterol or epinephrine), a toxin such as methanol or ethylene glycol, a vitamin deficiency (thiamine), diabetic ketoacidosis, a fast-growing cancer such as lymphoma or leukemia that lives on glycolysis, or a rare inherited mitochondrial disorder. Short bowel syndrome can cause a separate D-lactic acidosis from gut bacteria that standard assays do not detect.

The number matters. Between 2 and 4 mmol/L the usual response is to look for and correct the cause and repeat the test. Above 4, treatment is urgent: intravenous fluids, oxygen, antibiotics if infection is suspected, stopping culprit drugs, and treating the underlying problem. The trend is as important as the level; a lactate that falls by 10 to 20 percent or more within two to six hours is a reassuring sign, while a lactate that keeps rising despite treatment signals ongoing tissue injury and a much higher risk of death.

Common causes

Sepsis and septic shock
Infection drives lactate up through poor tissue perfusion, mitochondrial dysfunction and adrenaline-driven glycolysis. Lactate above 2 mmol/L with low blood pressure defines septic shock; above 4 triggers aggressive fluids, and each hour of delay in clearing it worsens survival.
Shock of any cause and severe dehydration
Bleeding, heart failure, heart attack, pulmonary embolism, severe vomiting or diarrhea and anaphylaxis cut oxygen delivery to tissues. Lactate rises before blood pressure falls in many patients, which is why it is used as an early warning.
Severe hypoxia and carbon monoxide or cyanide poisoning
Severe asthma, pneumonia, ARDS, cardiac arrest, drowning, carbon monoxide (which blocks oxygen carriage) and cyanide (which blocks mitochondrial use of oxygen) all produce high lactate; in cyanide poisoning a lactate above 8 to 10 mmol/L is a key clue.
Bowel or limb ischemia
A blocked mesenteric artery or a compartment syndrome produces a rising lactate with pain out of proportion to the examination; a normal lactate does not exclude early bowel ischemia, but a rising one is an alarm.
Seizures and extreme exercise
A generalised seizure can push lactate to 5 to 15 mmol/L, and a sprint or all-out effort to 15 to 25, through muscle glycolysis. Both clear within 1 to 2 hours, and a repeat sample shows the fall.
Metformin-associated lactic acidosis
Rare (around 3 to 10 cases per 100,000 patient-years, and no higher than with other diabetes drugs in Cochrane analysis) but serious, with mortality up to 30 to 50 percent. It occurs almost only when metformin accumulates because of acute kidney injury, dehydration, sepsis or liver failure, which is why metformin is paused during serious illness, before contrast scans and when eGFR falls below 30.
Liver disease and alcohol
The liver clears about 60 to 70 percent of lactate, so cirrhosis and acute liver failure let it accumulate. Alcohol metabolism pushes pyruvate toward lactate and blocks the liver's conversion of lactate back to glucose, so heavy drinking, especially with poor nutrition, raises lactate to 2 to 5 mmol/L.
Thiamine (vitamin B1) deficiency
Thiamine is needed by the enzyme that moves pyruvate into the mitochondria; without it, pyruvate is shunted to lactate. Seen in alcohol dependence, malnutrition, after bariatric surgery, hyperemesis of pregnancy and prolonged intravenous feeding. Lactate can be very high and falls within hours of intravenous thiamine.
Medicines and toxins
Inhaled or intravenous albuterol and epinephrine (through adrenaline-driven glycolysis), linezolid, propofol infusions, older HIV nucleoside drugs (stavudine, didanosine), isoniazid, high-dose acetaminophen overdose, salicylates, methanol, ethylene glycol and cocaine all raise lactate without hypoxia.
Cancer, diabetic ketoacidosis and inherited metabolic disorders
Lymphoma, leukemia and large solid tumors generate lactate through glycolysis (the Warburg effect), sometimes causing a persistent type B lactic acidosis. DKA commonly runs 2 to 4 mmol/L. Mitochondrial diseases, pyruvate dehydrogenase deficiency and glycogen storage disorders present in childhood with persistently high lactate.

Symptoms that can go with it

Rapid, deep breathing (the body blowing off acid), with breathlessness
Nausea, vomiting and abdominal pain
Weakness, drowsiness, confusion or reduced consciousness
Fast heart rate, low blood pressure, cold or mottled skin and reduced urine output in shock
Fever, chills and a source of infection in sepsis
Severe abdominal pain out of proportion to tenderness in bowel ischemia; severe limb pain in compartment syndrome
Muscle cramps and heavy, aching muscles after extreme exertion (short-lived and harmless)

Low lactic acid

A lactate at or below the lower end of the range, around 0.5 mmol/L, simply means your tissues are well oxygenated and your liver is clearing lactate normally. It is the expected result in a healthy person at rest and has no clinical significance. Laboratories do not flag it, and no condition is diagnosed by a low lactate.

The only practical point is that a low or normal lactate is reassuring in someone being assessed for sepsis, shock or bowel ischemia, though it does not completely exclude early or localised problems, so clinicians repeat it if the picture is worrying.

Common causes

Normal rest and good perfusion
Healthy adults sitting quietly commonly run 0.5 to 1.0 mmol/L.
Sample handled promptly on ice or in a fluoride tube
Correct collection gives the true, lower value; plain tubes left at room temperature read higher.
Very low muscle mass or prolonged fasting
Less glycolytic tissue and lower glucose turnover produce slightly less lactate; of no consequence.

Symptoms that can go with it

None; a low lactate does not cause symptoms

Read it alongside

Blood gas (pH, bicarbonate, base excess) — tells whether a high lactate has produced acidosis and how severe it is.
Anion gap — lactic acidosis is a high-anion-gap acidosis; a high gap without high lactate points to ketones, kidney failure or toxic alcohols.
Glucose and ketones — to separate DKA from lactic acidosis, and to spot hypoglycemia in liver failure or alcohol excess.
Creatinine and eGFR — kidney failure both raises lactate and makes metformin dangerous.
ALT, AST, bilirubin and ammonia — liver failure reduces lactate clearance.
CBC and CRP — infection and sepsis as the driver; leukemia or lymphoma as a type B cause.
Troponin and ECG — cardiogenic shock and heart attack as the cause of poor perfusion.
Thiamine level (or a therapeutic trial of thiamine) — in anyone with alcohol dependence, malnutrition or unexplained lactic acidosis.

What usually happens next

A mildly raised lactate (2 to 4 mmol/L) with no obvious illness is repeated on a correctly collected sample (gray-top tube or on ice, short tourniquet, at rest); many such results normalize.
A lactate above 4 mmol/L, or any raised lactate with low blood pressure, fever, breathlessness or confusion, is treated as an emergency: intravenous fluids, oxygen, cultures and antibiotics if infection is likely, and a search for the cause.
In sepsis and shock the lactate is remeasured every 1 to 2 hours; a fall of at least 10 to 20 percent within 2 to 6 hours is the target and guides further fluids or vasopressors.
If you take metformin and have had a high lactate, expect it to be paused during the illness and your kidney function rechecked before it is restarted; the same applies to other culprit medicines.
A persistently high lactate with a normal circulation leads to tests of liver function, thiamine status, medication review, and in some cases a search for cancer or an inherited metabolic disorder.

Diet, lifestyle and natural levers with evidence

What can move Lactate once the cause is known. Nothing here replaces finding the cause.

Endurance training raises your lactate threshold

Moderate evidence

Regular aerobic training increases mitochondrial capacity and lactate clearance, so lactate accumulates later and at a higher workload. The lactate threshold typically sits at 50 to 60 percent of maximal oxygen uptake in untrained people and 75 to 85 percent in trained endurance athletes, and 8 to 12 weeks of training shifts it measurably. This changes lactate during exercise, not the resting level, which is already normal in healthy people.

A blood test taken within an hour or two of hard training will still show a high lactate; rest before testing.

Thiamine (vitamin B1) when deficiency is the cause

Strong evidence

In thiamine deficiency, pyruvate cannot enter the mitochondria and is converted to lactate. Case series in alcohol dependence, after bariatric surgery, in hyperemesis of pregnancy and on long-term intravenous feeding show lactate levels of 5 to 15 mmol/L falling to normal within hours of intravenous thiamine, which is why thiamine is given routinely to at-risk patients with unexplained lactic acidosis. Dietary sources include whole grains, pork, legumes and fortified cereals.

Reduce heavy alcohol use

Moderate evidence

Ethanol metabolism raises the ratio of NADH to NAD in the liver, pushing pyruvate toward lactate and blocking the conversion of lactate back to glucose. Heavy drinkers commonly run lactate of 2 to 5 mmol/L during and after binges, and alcohol-related liver disease reduces clearance long term. Lactate normalizes with abstinence as liver function recovers.

Know the medicines that raise lactate

Strong evidence

No supplement lowers lactate, but several common medicines raise it: metformin (mainly when kidney function falls or during dehydration and serious illness), inhaled or nebulised albuterol in high doses, linezolid, propofol, older HIV nucleoside drugs and high-dose aspirin. Keeping well hydrated during vomiting or diarrhea, and pausing metformin on sick days and before contrast scans as advised, prevents most cases of metformin-associated lactic acidosis.

Never stop a prescribed medicine on your own because of a lactate result; the decision depends on kidney function and the clinical picture.

When to see a clinician promptly

A lactate above 4 mmol/L on any report is an emergency until the cause is known; if you are at home with this result, go to an emergency department.
Rapid deep breathing, confusion, drowsiness, cold mottled skin or very low urine output, with or without a known lactate: signs of shock or severe acidosis, call emergency services.
Fever or a known infection with a fast heart rate, low blood pressure or feeling very unwell: possible sepsis, where early treatment within the first hours saves lives.
If you take metformin and develop persistent vomiting, diarrhea, abdominal pain, muscle cramps, unusual sleepiness or fast breathing: possible metformin-associated lactic acidosis, same-day care.
Severe abdominal pain that seems worse than the examination suggests, especially in older people or with atrial fibrillation: possible bowel ischemia.
A persistently raised lactate (2 to 4 mmol/L) on repeat testing with no explanation, which needs assessment of liver, kidney, thiamine status and medicines.

Frequently asked questions

What is a normal lactic acid level?

A normal venous lactate is about 0.5 to 2.2 mmol/L, which is 4.5 to 20 mg/dL; arterial samples run slightly lower, about 0.5 to 1.6 mmol/L. Laboratory ranges differ a little, so use the one on your report. Levels between 2 and 4 mmol/L are called hyperlactatemia and need a cause; above 4 mmol/L with a low pH is lactic acidosis.

What lactate level is dangerous?

A lactate above 4 mmol/L is treated as an emergency in anyone who is unwell, because it indicates tissues are not getting enough oxygen or blood flow or that a serious metabolic problem is present. In sepsis, a lactate of 2 or more with low blood pressure defines septic shock, and levels above 4 carry a mortality around 25 to 30 percent. Values above 8 to 10 mmol/L are associated with very high mortality unless the cause is reversed quickly; the exceptions are the brief rises after a seizure or an all-out sprint.

What is lactic acidosis?

Lactic acidosis is a build-up of lactate in the blood (over 4 mmol/L) severe enough to lower the blood pH below 7.35. Type A occurs when tissues lack oxygen or blood flow (shock, sepsis, cardiac arrest, severe lung disease, bowel ischemia). Type B occurs without hypoxia, from liver failure, metformin accumulation, alcohol, thiamine deficiency, certain drugs and toxins, cancer or inherited metabolic disorders. Symptoms include rapid breathing, nausea, weakness and confusion, and the treatment is to correct the cause.

Can exercise raise lactic acid on a blood test?

Yes, dramatically but briefly. Hard exercise makes muscle switch to anaerobic metabolism, and a sprint or all-out effort can push lactate to 15 to 25 mmol/L, with moderate workouts producing 3 to 8. Levels return to baseline within one to two hours of rest. If your test was taken soon after exercise, a repeat at rest will show your true level. Resting lactate is normal in athletes; training raises the workload at which lactate starts to climb.

Does metformin cause high lactic acid?

Metformin slightly increases lactate production, and in rare circumstances this leads to metformin-associated lactic acidosis, at a rate of roughly 3 to 10 cases per 100,000 patient-years; a Cochrane review found the rate no higher than with other diabetes drugs. It occurs almost only when metformin accumulates because of acute kidney injury, dehydration, sepsis or liver failure. That is why metformin is paused on sick days with vomiting or diarrhea, before iodinated contrast scans and when eGFR falls below 30. Taken as prescribed with normal kidney function it is safe.

Why was my lactate checked in the emergency room?

Lactate is one of the fastest ways to tell how sick someone is. In suspected sepsis, bleeding, shock, severe breathing problems, poisoning or abdominal pain, a raised lactate shows that tissues are under-perfused, often before blood pressure drops, and a repeat one to two hours later shows whether fluids, oxygen and antibiotics are working. A lactate that falls by 10 to 20 percent or more is a good sign; one that keeps rising means the cause has not yet been controlled.

What is the difference between lactic acid and LDH?

Lactic acid (lactate) is the molecule; lactate dehydrogenase (LDH) is the enzyme that makes it from pyruvate. The lactate test measures how much lactic acid is in your blood and reflects oxygen delivery and metabolism right now. The LDH test measures how much of the enzyme has leaked out of damaged cells and reflects tissue injury or rapid cell turnover. They are ordered for different reasons and do not rise and fall together.

What does a low lactate mean?

Nothing to worry about. A lactate near the bottom of the range, around 0.5 mmol/L, means your tissues are well oxygenated and your liver is clearing lactate normally, which is the expected finding at rest. There is no condition caused or indicated by a low lactate, and laboratories do not flag it.

References

Lactic acid test. MedlinePlus, US National Library of Medicine (2023)View source
Kraut JA, Madias NE. Lactic acidosis. New England Journal of Medicine (2014)
Andersen LW, Mackenhauer J, Roberts JC, Berg KM, Cocchi MN, Donnino MW. Etiology and therapeutic approach to elevated lactate levels. Mayo Clinic Proceedings (2013)
Singer M, Deutschman CS, Seymour CW, et al.. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA (2016)
Evans L, Rhodes A, Alhazzani W, et al.. Surviving Sepsis Campaign: international guidelines for management of sepsis and septic shock 2021. Critical Care Medicine (2021)
Shapiro NI, Howell MD, Talmor D, et al.. Serum lactate as a predictor of mortality in emergency department patients with infection. Annals of Emergency Medicine (2005)
Salpeter SR, Greyber E, Pasternak GA, Salpeter EE. Risk of fatal and nonfatal lactic acidosis with metformin use in type 2 diabetes mellitus. Cochrane Database of Systematic Reviews (2010)
DeFronzo R, Fleming GA, Chen K, Bicsak TA. Metformin-associated lactic acidosis: current perspectives on causes and risk. Metabolism (2016)
Goodwin ML, Harris JE, Hernández A, Gladden LB. Blood lactate measurements and analysis during exercise: a guide for clinicians. Journal of Diabetes Science and Technology (2007)
Faude O, Kindermann W, Meyer T. Lactate threshold concepts: how valid are they?. Sports Medicine (2009)
Astles R, Williams CP, Sedor F. Stability of plasma lactate in vitro in the presence of antiglycolytic agents. Clinical Chemistry (1994)
Lactic acidosis (metabolic acidosis). Merck Manual Professional Version (2024)

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This page is educational and is not medical advice or a diagnosis. Lab results have to be interpreted together with your history, symptoms and other results by a clinician who knows you. Do not start or stop a supplement to change a lab value before the cause is known.