Can you take L-arginine with Cialis or tadalafil?

Can you take L-arginine with Cialis or tadalafil? Neither the Australian Cialis leaflet nor the tadalafil label names L-arginine, and in small trials men took the two together every day for 6 to 12 weeks. The pair raised erection scores a little more than either alone. Two cautions matter more: both lower blood pressure a little, and some "natural" sex supplements sold in Australia have been found to contain undeclared tadalafil. Tell the doctor who prescribes your tadalafil that you take it.

Is L-arginine one of the "nitrates" Cialis must not be taken with?

No. The nitrates the Cialis leaflet rules out are medicines for angina and other heart conditions — glyceryl trinitrate, isosorbide mononitrate and sodium nitroprusside — and the "poppers" amyl and butyl nitrite (Cialis CMI). Tadalafil strengthens the blood-pressure-lowering effect of nitrates, which is why "any form of organic nitrate" is ruled out (EMA — Cialis product information). L-arginine, an amino acid sold as a supplement, is not on that list or among the interactions the leaflet names, though the leaflet asks you to mention "any medicines, vitamins or supplements that you buy without a prescription".

Why do people combine them?

Because both are tied to nitric oxide, the chemical that starts an erection. Tadalafil works when sexual stimulation releases nitric oxide in the penis (EMA — Cialis). L-arginine is promoted as the raw material for nitric oxide, though whether extra L-arginine raises it in penile tissue is disputed — in rat penile muscle cells it did not (Ferrini et al., Nitric Oxide 2019). On its own, L-arginine may help mild to moderate ED more than placebo, in a meta-analysis of 10 small trials (Rhim et al., J Sex Med 2019); the detail is in using L-arginine for erectile dysfunction.

What did trials of L-arginine plus tadalafil find?

A modest extra gain, in small, short studies. In the largest, 300 men were randomised to daily L-arginine 2,500 mg, daily tadalafil 5 mg or both for 12 weeks; erectile-function scores rose from about 15 to 18 on L-arginine, to 21 on tadalafil and to 22 on both (Gallo et al., Sex Med 2020). A double-blind trial in 108 men with diabetes and mild to moderate ED, and a single-blind six-week trial in 120 men aged 60 or over taking L-arginine 5 g, also found the pair better than either alone (El Taieb et al., J Sex Med 2019; Abu El-Hamd and Hegazy, Andrologia 2020). A 2021 meta-analysis of four trials (373 men) agreed, found PDE5 inhibitors alone better than L-arginine alone, and found no clear difference in side effects between the pair and a PDE5 inhibitor alone (Xu et al., Andrologia 2021). The trials that state the dose used tadalafil 5 mg once a day, not the 10 or 20 mg tablet taken before sex.

Does the pair lower blood pressure too much?

The trial summaries report no problem, but it is the thing to watch. L-arginine on its own lowered blood pressure by about 6 mmHg systolic and 3 mmHg diastolic in a meta-analysis of 22 trials (Shiraseb et al., Adv Nutr 2022). Tadalafil's effect in healthy men is small — a mean maximal fall of 1.6/0.8 mmHg lying down — but in men already on blood-pressure medicines it "may induce a blood pressure decrease", and with the alpha-blocker doxazosin it is not recommended (EMA — Cialis). The Cialis leaflet rules tadalafil out if your blood pressure "is unusually high or low or is not effectively treated" (Cialis CMI). If you take blood-pressure tablets or feel faint on the pair, tell your prescriber. More in does tadalafil lower blood pressure?

Is the supplement what the label says?

Not always — the real risk. In June 2026 the TGA reported that testing of sexual enhancement products "that claimed to be dietary supplements or natural formulas" found "undeclared prescription-only substances sildenafil, tadalafil and dapoxetine"; none of the eleven products was on the Australian register (TGA safety advisory). With your prescribed tadalafil, a product like that is a second dose of a PDE5 inhibitor: the Cialis leaflet says not to take Cialis more than once a day and lists other PDE5 inhibitors among its interactions (Cialis CMI). See why some "herbal" sex pills contain hidden medicines and the side effects and safety of herbal Viagra.

What about L-citrulline, "nitric oxide" boosters or Viagra?

Neither the Cialis nor the Viagra leaflet names L-citrulline either, and a "nitric oxide" booster is only as safe as what it contains, so read its ingredient list. L-citrulline alone is covered in is watermelon a natural Viagra? L-arginine with sildenafil has its own page, can L-arginine be taken with Viagra?, and what does interact with tadalafil is listed in interactions of Cialis with other medicines and supplements.

The short answer

No label rules out L-arginine with Cialis or tadalafil, and small trials found a modest extra benefit without a clear rise in side effects over tadalafil alone. Tell your prescriber, take care if your blood pressure runs low or you take blood-pressure tablets, never take tadalafil with nitrates, and avoid "natural" sex products that may hide tadalafil. Every natural option is ranked by evidence in natural alternatives to Viagra.