References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Weight gain has become one of the most discussed side effects of modern HIV treatment. Clinical studies consistently show that people starting integrase inhibitor-based regimens — particularly those containing dolutegravir or bictegravir — gain more weight on average than those on older drug classes. The reasons aren’t fully understood, and the impact varies widely between individuals.
Here’s what the evidence shows and what you can do.
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What the Studies Show
| Drug/Class | Weight Gain Trend |
|---|---|
| Dolutegravir | Higher average weight gain |
| Bictegravir (Biktarvy) | Similar to dolutegravir |
| TAF (vs TDF) | Slightly more weight gain with TAF |
| Efavirenz | Less weight gain (but more CNS side effects) |
| Rilpivirine | Moderate |
| Darunavir | Moderate |
Weight gain is most pronounced in people starting treatment for the first time, women, and people of Black African descent — though it can affect anyone.
Why Does It Happen?
The full explanation isn’t known. Contributing factors likely include:
- Return-to-health — effective treatment stops the body burning energy fighting HIV
- Drug effect — INSTIs may affect metabolism or fat storage through mechanisms not yet understood
- TAF vs TDF — switching from TDF (which has a mild weight-suppressing effect) to TAF often reveals additional gain
- Appetite increase — feeling better leads to eating more
Is It Dangerous?
Moderate weight gain isn’t usually dangerous on its own. However, significant gain can increase risk of:
- Type 2 diabetes
- Cardiovascular disease
- Joint problems
- Reduced quality of life and mental health impact
Your HIV clinic monitors blood sugar, cholesterol and blood pressure to catch metabolic complications early.
What You Can Do
- Don’t stop your medication — the health consequences of untreated HIV are far worse
- Exercise regularly — 150 minutes per week, including resistance training
- Eat well — focus on whole foods, portion control and reduced processed food
- Discuss switching — your HIV team may consider a different regimen if weight gain is significant
- Monitor — track weight trends and discuss at clinic visits
Read more: Weight management with HIV | Biktarvy | Diabetes and HIV
Frequently Asked Questions
Will I definitely gain weight on dolutegravir?
Not necessarily. Average weight gain varies widely — some people gain nothing, others gain several kilograms. Individual experience differs significantly from population averages.
Should I avoid integrase inhibitors because of weight gain?
For most people, the benefits of INSTIs (efficacy, tolerability, resistance barrier) outweigh the weight concern. Discuss your priorities with your HIV team.
Can switching drugs reverse weight gain?
Some people lose weight after switching from an INSTI to a different class. Results vary and switching has trade-offs that your HIV team will discuss.
Related reading
- Injectable HIV Treatment: Everything You Need to Know
- Are HIV Tests Accurate If You're on PrEP, PEP or ART?
- CD4/CD8 Ratio: What It Means and Why It Matters
- CD4 Counts Explained: What Your Numbers Mean
- Changing HIV Treatment: When, Why and How
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
