Quick reference
Scan this table first. Details for each row are below.
| What you're taking | Level | Short version |
|---|---|---|
| Cyclosporine | Avoid or discuss | Levels fall; give 3 hours after orlistat. Alli says do not use |
| Fat-soluble vitamins | Timing matters | Daily multivitamin, at least 2 hours apart |
| Levothyroxine | Timing matters | At least 4 hours apart; monitor thyroid function |
| Warfarin and anticoagulants | Caution | Vitamin K absorption may fall — monitor coagulation |
| Amiodarone | Caution | Exposure to amiodarone is reduced |
| Antiepileptic drugs | Caution | Convulsions reported — monitor frequency and severity |
| Antiretroviral drugs | Caution | Loss of virological control reported — monitor HIV RNA |
| Diabetes medicines | Caution | Weight loss may mean insulin or sulfonylurea doses fall |
Cyclosporine
The one interaction serious enough to keep people off orlistat entirely.
Cyclosporine
Avoid or discussOrlistat reduces cyclosporine plasma levels, and the two must not be taken at the same time.
The Xenical label reports a drug interaction study. It found lower cyclosporine levels in the blood when cyclosporine was taken together with orlistat. It says the two should not be given at the same time. It says to take cyclosporine 3 hours after orlistat. It also says to consider more frequent monitoring in patients whose cyclosporine levels are being measured. The over-the-counter Alli label goes further, with an organ transplant alert on the front of the Drug Facts. Do not use it if you have had an organ transplant. Orlistat interferes with the medicines used to prevent transplant rejection. And do not use it if you are taking cyclosporine.
Fat-soluble vitamins
Not a medicine you already take — one the labels ask you to add.
Vitamins A, D, E, K and beta-carotene
Timing mattersOrlistat reduces how much of some fat-soluble vitamins you take up. Both labels ask for a daily multivitamin, taken hours away from a dose.
Orlistat has been shown to reduce the absorption of some fat-soluble vitamins and of beta-carotene. So the Xenical label says patients should be strongly encouraged to take a multivitamin supplement containing fat-soluble vitamins, to ensure adequate nutrition. It says the supplement should be taken once a day, at least 2 hours before or after orlistat — at bedtime, for example. It notes that vitamin D and beta-carotene levels may already be lower in people with obesity. One study looked at how the body handles the drug. It showed reduced absorption of a beta-carotene supplement. It also showed blocked absorption of a vitamin E acetate supplement. The label says the effect on supplemental vitamin D, vitamin A and dietary vitamin K is not known. The Alli label puts it simply: take a multivitamin once a day, at bedtime.
Levothyroxine
A four-hour gap, and a thyroid check.
Levothyroxine
Timing mattersHypothyroidism has been reported when orlistat and levothyroxine were taken together.
Hypothyroidism means an underactive thyroid. The label says it has been reported since the drug went on the market. Those reports were in people treated with orlistat and levothyroxine at the same time. It says to take levothyroxine and orlistat at least 4 hours apart. It says to monitor patients taking both for changes in thyroid function. The Alli Drug Facts label lists thyroid disease medicine too. It is one of the prescription medicines to ask a doctor or pharmacist about before using orlistat.
Warfarin and other anticoagulants
The vitamin K link makes this one worth flagging early.
Warfarin and other anticoagulants
Use cautionVitamin K absorption may fall, and changes in coagulation have been reported.
The label says vitamin K absorption may be decreased with orlistat. It says there have been reports from people taking orlistat and anticoagulants together. Those reports are of decreased prothrombin, increased INR and unbalanced anticoagulant treatment. Those are all changes to haemostatic parameters — the measures of how the blood clots. Then comes the instruction. Some people are on chronic stable doses of warfarin or another anticoagulant. If they are prescribed orlistat, those measures should be monitored closely for changes. The Alli label lists anticoagulants as well — blood thinning medicine. They are among the prescription medicines to raise with a doctor or pharmacist first.
Amiodarone
A heart-rhythm medicine whose exposure falls when orlistat is added.
Amiodarone
Use cautionA study showed reduced exposure to amiodarone and its active metabolite during orlistat treatment.
The label reports a study in which amiodarone was swallowed during orlistat treatment. Exposure to amiodarone, and to its breakdown product desethylamiodarone, was reduced. The label says amiodarone may therefore have a reduced effect. It notes that starting orlistat in people already on a stable amiodarone dose has not been studied. The Alli Drug Facts label names amiodarone too, describing it as heart medicine. It is one to ask about before use.
Antiepileptic drugs
The label reports convulsions with this combination.
Antiepileptic drugs
Use cautionConvulsions have been reported in people taking orlistat together with antiepileptic medicines.
The Xenical label says convulsions have been reported. They came from patients treated with orlistat and antiepileptic drugs at the same time. It says patients should be monitored for possible changes. Those changes are in how often convulsions happen, or how severe they are. The Alli label reflects the same concern in its stop-use section. It says to stop use and ask a doctor if you are taking medicine for seizures and your seizures happen more often or get worse.
Antiretroviral drugs
A serious one if you are being treated for HIV.
Antiretroviral drugs
Use cautionLoss of virological control has been reported in people taking orlistat alongside HIV treatment.
The label says loss of virological control has been reported in HIV-infected patients taking orlistat with antiretroviral drugs. In other words, the HIV treatment stopped holding the virus down. The drugs named are atazanavir, ritonavir, tenofovir disoproxil fumarate and emtricitabine, plus the combinations lopinavir/ritonavir and emtricitabine/efavirenz/tenofovir disoproxil fumarate. The label says the exact mechanism is unclear. It may involve less of the antiretroviral drug being absorbed into the body. It says HIV RNA levels should be monitored frequently. And it says orlistat should be discontinued if there is a confirmed increase in HIV viral load. The Alli label names antiretrovirals among the prescription medicines to ask about first.
Diabetes medicines
Not a direct interaction — a consequence of losing weight.
Insulin and oral diabetes medicines
Use cautionWeight loss may affect blood sugar control, and doses may need to come down.
Weight loss may affect glycaemic control in people with diabetes, the label says. Glycaemic control means blood sugar control. It says some patients may need a lower dose of insulin. The same goes for a blood-sugar-lowering tablet such as a sulfonylurea. The Alli label lists diabetes medicine among the prescription medicines to discuss with a doctor or pharmacist before use. It notes that some prescription doses may need to be adjusted. Others may not work as well when used with orlistat.
The Alli over-the-counter warnings
Some of these do not appear on the prescription label
Alli is sold without a prescription. So its Drug Facts label front-loads the checks a prescriber would otherwise make. It says not to use Alli if you have had an organ transplant, or if you are taking cyclosporine. It also says not to use it if you have been diagnosed with problems absorbing food, or if you are not overweight. It says not to use it at all if you are pregnant or breastfeeding. It says to ask a doctor before use if you have ever had gallbladder problems, kidney disease, kidney stones or pancreatitis. And it says to ask a doctor or pharmacist first about a list of medicines. That list is anticoagulants, amiodarone, diabetes medicine, thyroid disease medicine, seizure medicine, antiretrovirals, and any other weight loss product.
Common questions
Written and maintained by one person · Built with agentic AI tools · Every number checked against the cited trial · Not medical advice
- Xenical (orlistat) prescribing information — Drug Interactions (7.1–7.7), Warnings and Precautions (5.1), Dosage and Administration (2, 2.1), Clinical Pharmacology (12.2) View source ↗
- alli (orlistat 60 mg) over-the-counter Drug Facts label — Warnings, Do not use, Ask a doctor or pharmacist before use, When using this product View source ↗
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