Nursing care
Why lactate rises in shock and what the trend tells the nurse
Written and reviewed by Dana Whitfield, RN, MSN · 4 min read · Updated October 2026
Short answer
In shock, tissues receive too little oxygen to run aerobic metabolism, so cells switch to anaerobic pathways that generate lactate. A poorly perfused liver also clears lactate more slowly. A rising lactate therefore signals ongoing tissue hypoperfusion, while a falling trend alongside better perfusion signs suggests resuscitation is working.
Trace lactate from low oxygen delivery to the blood
Cells normally make most of their energy aerobically, using oxygen in the mitochondria. Lactate is produced in small amounts all the time and is cleared mainly by the liver. When blood pressure, cardiac output or oxygen content falls far enough, the mitochondria cannot keep up, and cells rely on anaerobic glycolysis, which converts pyruvate to lactate.
At the same time, the liver, which would normally recycle lactate, is itself underperfused. Production rises while clearance falls, so blood lactate accumulates. The underlying problem is inadequate oxygen use at the cellular level, which can be present before blood pressure drops markedly. That is why lactate is valued as a marker of hidden hypoperfusion in sepsis and other shock states.
Know when a high lactate is not shock
Not every raised lactate means poor perfusion. Seizures, vigorous muscle activity, some medicines such as metformin, and liver failure can all raise lactate when oxygen delivery is adequate. Clinicians call perfusion-related lactate type A and the other forms type B. A difficult tourniquet draw or recent exercise can also affect the result, so specimen technique matters.
Because of this, the number must be read with the patient. A high lactate with hypotension, cool clammy skin, confusion and low urine output points strongly toward shock. A similar value in a patient who has just had a seizure but now looks well perfused may mean something different. The nurse reports both the result and the context.
Lactate is also a lagging, indirect signal. It reflects the balance between production and clearance, so a patient with liver dysfunction may clear it slowly even after perfusion improves. That is one more reason a single result should be weighed with mental status, skin, urine output and the overall direction of the patient's condition.
Use the trend to judge resuscitation
A single value tells you the patient has a problem; repeated values tell you whether treatment is helping. Serial lactate measurements are used during resuscitation alongside blood gases, creatinine and bedside signs. A falling lactate, warmer skin, improving mental status and rising urine output together suggest that oxygen delivery is catching up with demand.
A lactate that stays high or climbs despite fluids and other treatment is a warning that perfusion is still inadequate or that the source, such as infection or bleeding, is not controlled. Persistent hypoperfusion can progress to organ failure. Make sure repeat specimens are drawn at the ordered times and that results reach the provider rather than sitting unseen in the record.
Match bedside findings to the lactate picture
Assess mental status, capillary refill, skin temperature and colour, peripheral pulses, heart rate, blood pressure and hourly urine output. Oliguria below about half a millilitre per kilogram per hour is a common hypoperfusion marker. Trends matter more than single readings, and a rising heart rate or new restlessness can appear before blood pressure falls.
Nursing actions include supporting oxygenation, maintaining reliable intravenous access, giving prescribed fluids and medicines, and recording intake and output accurately. Escalate early when perfusion signs worsen. Local sepsis and shock protocols set how often lactate is repeated and which targets prompt further action, so exam answers that favour reassessment and escalation usually reflect that structure.
Work a hypothetical exam-style scenario
Imagine a patient with suspected sepsis who has received the prescribed fluid bolus. Blood pressure has improved slightly, but the repeat lactate is higher than the first, urine output remains low and the patient is newly drowsy. Options are to document improvement, slow the fluids, notify the provider of worsening perfusion, or encourage oral fluids.
Notifying the provider is best, because the rising lactate, low urine output and new drowsiness indicate continuing hypoperfusion despite a better blood pressure. Documenting improvement relies on one reassuring number. Slowing fluids is not supported by the findings. Oral fluids are unsafe in a drowsy patient and too slow for shock. The provider decides the next treatment.
Sources and further reading
MSD Manual Professional: Shock. Tissue hypoperfusion, shift to anaerobic metabolism, lactate as a perfusion marker, bedside signs and serial monitoring.
MSD Manual Professional: Lactic Acidosis. Type A and type B lactate elevation, reduced hepatic clearance in shock and non-perfusion causes.
MedlinePlus: Lactate Test. What lactate is, causes of high results including sepsis, and specimen factors such as exercise.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our dosage calculation and lab values practice questions are the closest set to what this page covers.
Common questions
Why does lactate rise before blood pressure falls?
Compensation such as vasoconstriction and a faster heart rate can hold blood pressure up while tissues are already short of oxygen, so lactate can climb first.
Can a patient have high lactate without shock?
Yes. Seizures, intense exercise, some medicines and liver failure can raise lactate with adequate perfusion. Interpret the result with the clinical picture.
What does a falling lactate mean during treatment?
A falling lactate together with better mental status, skin perfusion and urine output suggests resuscitation is improving oxygen delivery. One value alone is not enough.
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