If you have recently been prescribed Biktarvy — or are weighing it against other options — understanding its side effect profile is essential. The short answer is reassuring: Biktarvy is one of the best-tolerated HIV regimens ever studied, with fewer than 1% of patients stopping treatment due to side effects over five years. But every patient is different, and knowing what to watch for helps you stay ahead of any problems.
This guide covers every known side effect — common, uncommon, and serious — along with what causes them, how long they last, which drug interactions to avoid, and what your doctor should be monitoring. All data comes from Gilead’s five-year SOLSTICE and GS-US-380-1489 clinical program and the current FDA prescribing information for Biktarvy.
Biktarvy’s most common side effects are diarrhea, nausea, and headache — all mild and usually resolving within the first few weeks. In five-year clinical data, fewer than 1% of patients stopped treatment due to any adverse event. Serious side effects are rare but include lactic acidosis and hepatitis B flare on discontinuation.
- Fewer than 1% of patients stopped Biktarvy due to side effects over five years — one of the lowest discontinuation rates of any single-tablet HIV regimen.
- Most common effects (diarrhea, nausea, headache) are mild and typically resolve within the first 2–4 weeks. Taking with food reduces GI effects.
- Weight gain of 2–3 kg at week 48 is common and partly reflects healthy immune reconstitution.
- Rifampin and dofetilide are hard contraindications. St. John’s Wort and antacids require careful management.
- Patients co-infected with hepatitis B must never stop Biktarvy without medical supervision — abrupt discontinuation risks a serious HBV flare.
Common Side Effects of Biktarvy
In the pivotal Phase 3 clinical trials, the following side effects occurred in at least 3% of patients taking Biktarvy. All were considered mild to moderate in severity.
- Diarrhea — reported in approximately 7% of patients. Usually loose stools rather than frequent watery diarrhea. Often improves spontaneously after the first few weeks.
- Nausea — reported in approximately 6% of patients. Most common in the first week or two. Taking Biktarvy with food significantly reduces this effect.
- Headache — reported in approximately 6% of patients. Typically mild and resolves without any intervention.
- Fatigue — reported in around 4% of patients. Often difficult to distinguish from HIV-related fatigue, which itself improves as viral load is suppressed.
- Abnormal dreams — reported in approximately 3% of patients. More common in the first month and usually subsides.
- Dizziness — reported in approximately 3% of patients. Rare reason for stopping treatment.
Taking Biktarvy with food: Food increases bictegravir bioavailability and significantly reduces gastrointestinal side effects. Biktarvy can be taken with any meal — there is no food restriction. If nausea is an issue, a light snack is sufficient.
Full Biktarvy Side Effects Table
| Side Effect | Frequency | Severity | Typically Resolves |
|---|---|---|---|
| Diarrhea | ~7% | Mild | 2–4 weeks |
| Nausea | ~6% | Mild | 1–2 weeks |
| Headache | ~6% | Mild | 2–3 weeks |
| Fatigue | ~4% | Mild | Variable |
| Abnormal dreams | ~3% | Mild | 2–4 weeks |
| Dizziness | ~3% | Mild | Variable |
| Weight gain | Common | Moderate | Ongoing — monitor |
| Elevated LDL / cholesterol | Some patients | Moderate | Ongoing — monitor |
| Increased creatinine (renal) | Some patients | Moderate | Ongoing — monitor |
| Lactic acidosis | Rare | Serious | Stop drug — seek care |
| Severe hepatomegaly / steatosis | Rare | Serious | Stop drug — seek care |
| Hepatitis B flare (on stopping) | HBV co-infection | Serious | Do not stop without MD |
Weight Gain and Metabolic Effects
Weight gain is one of the most discussed side effects of integrase inhibitor-based regimens, including Biktarvy. In clinical trials of treatment-naive patients, average weight increased by approximately 2–3 kg at week 48. The cause is not fully understood, but it is partly a class effect of integrase inhibitors and partly immune reconstitution weight recovery — patients who were underweight due to untreated HIV regain healthy mass as their immune system recovers.
For patients with pre-existing obesity, diabetes risk, or cardiovascular disease, clinically significant weight gain should be monitored and managed. Modest changes in cholesterol and triglycerides are also possible and are tracked as part of routine HIV care. For a full breakdown of weight trajectory, lipid changes, and metabolic management over time, see the dedicated guide below.
Weight gain, lipid changes, and long-term metabolic effects — including 5-year phase 3 data — are covered in full on the Biktarvy Long-Term Side Effects page.
For specific guidance on managing weight gain, see Biktarvy Weight Gain: What to Expect.
Serious Side Effects and Boxed Warnings
The FDA prescribing information for Biktarvy carries a boxed warning — the most serious warning the FDA issues — covering two distinct situations.
Lactic acidosis and severe hepatomegaly with steatosis
This is a class effect of nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs). Lactic acidosis is an accumulation of lactic acid in the blood and can be life-threatening. Cases are rare but have been reported with all NRTI-containing regimens.
Seek immediate medical attention if you experience: unexplained muscle pain or weakness, difficulty breathing, stomach pain, nausea or vomiting that is getting worse, feeling cold especially in your arms and legs, dizziness, or irregular heartbeat. These may be signs of lactic acidosis.
Post-treatment hepatitis B exacerbation
If a patient co-infected with both HIV and hepatitis B (HBV) abruptly stops Biktarvy, the sudden loss of HBV suppression can trigger a severe and potentially life-threatening hepatitis B flare. Any patient with HBV co-infection must never stop Biktarvy without close medical supervision. All patients should be tested for hepatitis B before starting.
All patients should be tested for hepatitis B before starting Biktarvy. If co-infection is present, your doctor needs to factor this into any future treatment changes.
Drug Interactions to Know
Bictegravir is metabolized by the CYP3A and UGT1A1 enzymes. This creates several important drug interactions that every patient should be aware of. For the full clinical interaction guide, see our dedicated Biktarvy drug interactions page.
Contraindicated drugs (must NOT be taken with Biktarvy)
- Rifampin — reduces bictegravir plasma levels by approximately 75%, rendering Biktarvy ineffective. Do not co-administer.
- Dofetilide — Bictegravir inhibits renal transporters that clear dofetilide, leading to dangerously elevated dofetilide levels and risk of serious cardiac arrhythmia.
Drugs requiring caution or separation
- Rifabutin — reduces bictegravir levels by approximately 38%. Not recommended.
- St. John’s Wort — strong CYP3A inducer. Can significantly reduce bictegravir levels. Do not use while on Biktarvy.
- Antacids and supplements containing aluminum, magnesium, iron, or calcium — chelate bictegravir in the gut, reducing absorption. Separate Biktarvy from these products by at least 2 hours. This includes common antacids (Maalox, Tums), iron supplements, and most multivitamins.
- Metformin — Biktarvy can increase metformin plasma levels. If you take metformin, your doctor should monitor for toxicity and may need to adjust the dose.
Always tell every prescriber you take Biktarvy. This includes dentists, urgent care providers, and any specialist prescribing new medications. The drug interaction risk is real and occasionally missed in non-HIV clinical settings.
How Long Do Biktarvy Side Effects Last?
For the vast majority of patients, early side effects are temporary. The typical timeline:
- Week 1–2: Nausea and headache are most likely to occur. Taking Biktarvy with food significantly reduces nausea during this window.
- Week 2–4: Most GI side effects resolve as the body adjusts. Abnormal dreams and dizziness also typically improve.
- Beyond week 4: Most patients report no ongoing side effects. Fatigue often improves substantially as viral load is suppressed over the first several months.
- Weight and metabolic changes: These develop gradually over months to years and require ongoing monitoring — see the long-term side effects guide for the full picture.
If significant side effects persist beyond four to six weeks, or if any new symptoms develop at any point, speak with your HIV care provider.
What Your Doctor Should Monitor
Routine monitoring on Biktarvy, as recommended by DHHS HIV treatment guidelines, covers HIV viral load and CD4 count, renal function (creatinine, eGFR, urinalysis), liver enzymes, fasting lipids, glucose and HbA1c, body weight, and hepatitis B serology. Most labs are done at baseline and then every 6–12 months once viral suppression is established.
The complete monitoring timeline — including what to test, when, and why, with organ-system breakdowns for kidney, bone, and metabolic markers — is on the Biktarvy Long-Term Side Effects page.
Common Mistakes Patients Make
Stopping the medication without telling their doctor
This is the most dangerous mistake, particularly for patients co-infected with hepatitis B. Always call your provider before stopping.
Attributing ongoing fatigue to Biktarvy when another cause is more likely
Fatigue has many causes — sleep quality, depression, anaemia, thyroid issues, and others. If fatigue is an issue, ask your doctor for a full workup rather than assuming it is the medication.
Taking antacids or supplements at the same time as Biktarvy
Multivitamins, iron tablets, calcium supplements, and over-the-counter antacids should all be separated from Biktarvy by at least two hours. Build this separation into your daily routine.
Not disclosing Biktarvy to new prescribers
Drug interactions can occur when seeing an urgent care clinic, a new specialist, or a dentist. Always mention Biktarvy — or carry a full medication list. The rifampin and dofetilide interactions in particular occur in settings where the prescriber may not be thinking about HIV drug interactions.
Assuming weight gain is always a problem
In most cases, especially in the first year, modest weight gain reflects immune reconstitution and return of appetite — both healthy signs. Work with your care team to distinguish normal recovery from metabolically problematic weight change.
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- Gilead Sciences. Biktarvy US Prescribing Information. 2024. accessdata.fda.gov
- Gallant J, et al. Bictegravir, emtricitabine, and tenofovir alafenamide versus dolutegravir, abacavir, and lamivudine: 96-week results. Lancet HIV. 2018;5(11):e567–e578.
- DHHS Panel on Antiretroviral Guidelines for Adults and Adolescents. Updated January 2025. clinicalinfo.hiv.gov
- Sax PE, et al. B/F/TAF in treatment-naive adults: week 240 results. CROI 2023; Abstract 152.
- Stellbrink HJ, et al. Long-term kidney safety with B/F/TAF: pooled phase 3 analysis. AIDS. 2022;36(12):1691–1700.