The short answer
Iron can lower dolutegravir absorption if both are taken together while fasting. Current TIVICAY instructions allow simultaneous iron supplementation with food; otherwise, dolutegravir should come at least two hours before or six hours after iron.
What this answer covers
Oral dolutegravir tablets and oral iron supplements. Direct research used ferrous fumarate, not every iron salt, injected iron or every combination antiretroviral formulation.
- Supplement or preparation
- iron
- Medication ingredient
- dolutegravir
How large was the measured effect?
In a small healthy-adult crossover study, simultaneous fasting ferrous fumarate reduced dolutegravir exposure by about 54%. The 324 mg salt dose contained approximately 107 mg elemental iron. This is a pharmacokinetic finding, not a measured 54% reduction in HIV treatment success.
Can a meal prevent the absorption problem?
In the experiment, taking both with a moderate-fat meal counteracted the exposure decrease. Giving dolutegravir two hours before iron also worked in the tested fasting schedule. These results support the labeled options; they do not establish every meal size or every iron formulation.
Why is two hours apart not enough detail?
The ordering changes the recommendation. Dolutegravir may be taken at least two hours before iron, but should be delayed at least six hours after iron when fasting. The prescription instructions also include the simultaneous-with-food option for TIVICAY tablets.
What if I need iron for anemia?
Ask your HIV pharmacist to fit the necessary supplement into the full regimen. Check the iron amount and any minerals in prenatal or multivitamin products. Do not stop necessary treatment or add an extra antiretroviral dose on your own; product-specific scheduling is the practical issue.
Evidence and practical considerations
Absorption & effectiveness
Iron can lower dolutegravir absorption if both are taken together while fasting. Current TIVICAY instructions allow simultaneous iron supplementation with food; otherwise, dolutegravir should come at least two hours before or six hours after iron.
- Exact scope
- Oral dolutegravir tablets and oral iron supplements. Direct research used ferrous fumarate, not every iron salt, injected iron or every combination antiretroviral formulation. with Dolutegravir, exact RxCUI 1433868, IN. TIVICAY contains dolutegravir sodium expressed as dolutegravir active-moiety strength in its label. This provides the explicit salt-to-IN bridge. Oral tablets are the primary scope; no automatic extrapolation to another integrase inhibitor or a different combination regimen. TIVICAY PD is not interchangeable milligram for milligram.
- Medication form and route
- oral
What remains uncertain
- The trial used ferrous fumarate in healthy adults and did not test injected iron or long-term virologic outcomes. Current label guidance, rather than a direct six-hour trial arm, supplies that separation option.
Factors that may matter: exact preparation and dose; food and administration order; complete antiretroviral regimen.
Read the supporting source summaries
Source 1: regulatory prescribing information
dailymed.nlm.nih.gov · Source check Sep 10, 2026
Population: People prescribed oral dolutegravir, including tablet and pediatric suspension formulations with separate dosing instructions.
Specifies dolutegravir two hours before or six hours after named mineral products; calcium/iron supplements have a simultaneous-with-food exception for TIVICAY. St. John’s wort co-use is to be avoided because a dosing recommendation cannot be established.
How this applies: Restricted to the preparation and conditions described in this article.
The table includes both measured and predicted interactions. It does not quantify every mineral salt, product or botanical extract. Formulations and combination tablets require their own instructions.
Source 2: primary human pharmacokinetic trial
accp1.onlinelibrary.wiley.com · Source check Sep 10, 2026
Population: Twenty-four healthy adults enrolled in an open-label crossover trial; twenty-one completed the planned study.
Fasting simultaneous dosing reduced dolutegravir AUC by 39% with calcium and 54% with iron. A meal or giving dolutegravir two hours first counteracted the decrease.
How this applies: Restricted to the preparation and conditions described in this article.
Single-dose pharmacokinetics, not a long-term HIV outcome trial. Does not compare all calcium/iron salts or test the six-hours-after schedule directly. Industry-funded study; authors reported employment and stock options.
Source 3: government clinical guideline
clinicalinfo.hiv.gov · Source check Sep 10, 2026
Population: Adults and adolescents receiving antiretroviral therapy.
Supports product-specific spacing and the calcium/iron food exception; says not to coadminister St. John’s wort with dolutegravir.
How this applies: Restricted to the preparation and conditions described in this article.
Clinical guidance combines measured and predicted effects. The DTG supplement instructions specifically discuss calcium and iron; the zinc heading is not a zinc-only human experiment.
Research assessment: · Open full citations ↗
Review and change history
- Publication status
- Published research summary
- Clinical review
- Not yet recorded
| Date | Update |
|---|---|
| Article prepared | |
| Current prescribing instructions and original research checked. Article written with product-specific timing and explicit limits of the evidence. | |
| Research summary published |
Article revision: 22a06b47a672aba4
This guide brings together the evidence records used by our interaction checker. Each finding retains its own preparation limits, research date, and source summaries.
Full citations require verification. Reading this answer and the source summaries does not.
Taking other supplements or medications?
Use the checker to explore your other combinations. Ask a pharmacist to review the exact products, amounts and medical conditions in your complete list.
Open the interaction checkerInformation, not medical advice. Do not change prescribed treatment based on this guide.