Can tenofovir-based pre‑exposure prophylaxis (PrEP) cause lactic acidosis?

Can Tenofovir-Based PrEP Cause Lactic Acidosis?

Lactic acidosis is a recognized but rare complication of tenofovir-based medications, including those used for PrEP, though it occurs much less commonly with short-term PrEP use compared to long-term HIV treatment. 1, 2

Understanding the Risk

The most recent CDC guidelines (2025) explicitly acknowledge that mitochondrial toxicity is a hallmark adverse effect of the NRTI class (which includes tenofovir), and this can manifest as lactic acidosis 1. However, the context matters significantly:

Risk Stratification

For PrEP specifically (short-term prophylaxis):

• The risk is substantially lower than with long-term HIV treatment because PrEP involves shorter exposure durations
• No cases of lactic acidosis have been reported in major PrEP trials 3
• The 2012 CDC PrEP guidelines do not list lactic acidosis as a monitoring parameter for healthy PrEP users 3

For treatment regimens (long-term use):

• Lactic acidosis risk is well-documented but still rare (incidence <1% annually) 4
• Risk increases with certain patient characteristics and drug combinations

High-Risk Scenarios to Recognize

You must be vigilant for lactic acidosis in patients with:

• Renal impairment - tenofovir accumulation dramatically increases risk 2, 5, 6
• Low body weight - leads to higher plasma concentrations 6
• Concurrent nephrotoxic medications (NSAIDs, boosting agents like cobicistat/ritonavir) 2, 6
• Hepatic disease - particularly cirrhosis or hepatic steatosis 4, 2
• Pregnancy - especially third trimester with combination regimens 7, 8

Clinical Presentation

Early symptoms are nonspecific and easily missed:

• Fatigue, nausea, vomiting, abdominal pain
• Diffuse myalgia and muscle weakness 6
• Progressive dyspnea
• Altered mental status in severe cases 5

Laboratory findings:

• Elevated serum lactate (>2 mmol/L warrants close monitoring; >5 mmol/L is critical) 4
• Normal anion gap or high anion gap metabolic acidosis
• Elevated hepatic transaminases (suggesting hepatic steatosis) 4, 2
• Elevated creatinine (may indicate concurrent renal toxicity) 2

Monitoring Strategy

Before starting tenofovir-based PrEP:

• Calculate creatinine clearance (must be ≥60 mL/min for standard dosing) 3, 2
• Assess hepatitis B/C status 3
• Screen for risk factors listed above

During PrEP use:

• Check serum creatinine at 3 months, then every 6 months 3
• Do NOT routinely monitor lactate in asymptomatic, healthy PrEP users - this is not recommended 3
• DO check lactate immediately if patient develops unexplained symptoms (fatigue, nausea, myalgia, dyspnea) 4, 2

For high-risk patients (renal impairment, low BMI, hepatic disease):

• More frequent creatinine monitoring (every 2-3 months)
• Lower threshold to check lactate with any new symptoms
• Consider alternative PrEP options (injectable cabotegravir or lenacapavir) 9

Management of Suspected Lactic Acidosis

If lactate >5 mmol/L or symptomatic hyperlactatemia:

1. Immediately discontinue tenofovir 2
2. Obtain arterial blood gas to confirm acidosis 4
3. Check hepatic enzymes and renal function 2
4. Initiate supportive care (may require continuous renal replacement therapy in severe cases) 5, 10
5. Consider L-carnitine and thiamine supplementation 5

Critical Pitfalls to Avoid

• Do not dismiss vague symptoms (fatigue, nausea, myalgia) in patients on tenofovir - check lactate 4, 2
• Do not continue tenofovir in patients with declining renal function - adjust dose or switch agents 2
• Do not combine tenofovir with multiple nephrotoxic agents without very close monitoring 2
• Do not confuse this with pregnancy-related conditions (acute fatty liver, HELLP syndrome) in pregnant patients - they can appear similar 7, 8

Tenofovir Formulation Differences

Tenofovir alafenamide (TAF) vs. tenofovir disoproxil fumarate (TDF):

• TAF achieves lower plasma tenofovir concentrations and has less renal toxicity 1
• However, lactic acidosis has been reported with both formulations 5, 10, 11
• TAF may have a lower incidence, but the risk is not eliminated 10

Bottom Line for PrEP Practice

For healthy individuals without risk factors taking PrEP, lactic acidosis is extremely rare and routine lactate monitoring is not indicated. However, maintain a high index of suspicion in patients with renal impairment, low body weight, hepatic disease, or those on nephrotoxic medications. Any unexplained symptoms warrant immediate lactate measurement and consideration of stopping tenofovir. 1, 3, 1, 2