Aspirin: How Low Can You Go?

After revisiting aspirin indications earlier this month I received a few excellent questions that prompted me to delve further into the mysteries of this remarkable anti-platelet drug.

First, T.D. Murray asked:

Hello Dr. P. Thanks for your very informative website. I have read that as little as 30 mg. of aspirin per day is sufficient to slow coagulation. One of my cardiologists states that the lowest effective dosage for aspirin has not been established. Would lower dosage cause fewer side effects? Your thoughts please.

After scanning the literature I could only find one study supporting a 30 mg dosage in secondary prevention, the Dutch TIA trial which found no difference in efficacy between 30 mg and 283 mg aspirin and less bleeding at the lower dosage.

“In the group assigned to receive 30 mg of aspirin, the frequency of death from vascular causes, nonfatal stroke, or nonfatal myocardial infarction was 228 of 1555 (14.7 percent), as compared with 240 of 1576 (15.2 percent) in the group assigned to receive 283 mg. The age- and sex-adjusted hazard ratio for the group receiving the lower dose was 0.91 (95 percent confidence interval, 0.76 to 1.09). There were slightly fewer major bleeding complications in the 30-mg group than in the 283-mg group (40 vs. 53), and significantly fewer reports of minor bleeding (49 vs. 84). Fewer patients receiving 30 mg of aspirin reported gastrointestinal symptoms (164 vs. 179) and other adverse effects (73 vs. 90).”

There aren’t a lot of studies with that low a dosage and I haven’t found any comparing 30 to what has become the standard-81 mg.

Most of the these aspirin trials in secondary prevention took place in the 1980s and 1990s before the era of widespread statin usage, better blood pressure control, and early and effective treatment of MI so may not be applicable in our current medical environment.

A 2002 review concluded:

Within a few days of beginning 75 mg aspirin daily, cyclo-oxygenase is virtually completely inhibited in platelets, producing an antithrombotic effect. The present analyses indicate that high doses of 500-1500 mg aspirin daily (which are more gastrotoxic) are no more effective than medium doses of 160-325 mg/day or low doses of 75-150 mg/day (figs 5 and 6). Results from trials of lower doses are less conclusive. Hence, the available evidence supports daily doses of aspirin in the range 75-150 mg for the long term prevention of serious vascular events in high risk patients. In clinical situations where an immediate antithrombotic effect is required (such as acute myocardial infarction, acute ischaemic stroke, unstable angina), a loading dose of about 150-300 mg, which is sufficient to produce rapid and complete inhibition of thrombox- ane mediated platelet aggregation, should probably be given.

Unacceptable Bleeding on Aspirin

I’ve had patients develop unacceptable bruising or bleeding issues on 81 mg aspirin and we’ve agreed to trial lower dosages.

I describe in detail my own experience when i cut my philtrum shaving and bled seemingly for ever here.

In that post I discussed various tests and devices that had been proposed to monitor platelet activity on aspirin but none of these are utilized by anyone I know. It is entirely possible that 30 mg aspirin is the perfect dosage for T.D. Murray but an imperfect one for someone else based on individual pharmacokinetics.

Bottom line, I would say, is that 30 mg may be just as effective as doses >75 mg but unless you have concerns about bleeding or gastric irritation on the higher dosage you are best served by staying with the dosage that has been studied extensively and found to be effective in the largest number of patients.

Clopidogrel as an Alternate

One option to consider is clopidogrel at 75 mg daily which according to this recent Korean study in patients > 1 year after a coronary stent, appears to have less bleeding issues than aspirin.

Clopidogrel monotherapy, compared with aspirin monotherapy during the chronic maintenance period after percutaneous coronary intervention with DES significantly reduced the risk of the composite of all-cause death, non-fatal myocardial infarction, stroke, readmission due to acute coronary syndrome, and BARC bleeding type 3 or greater.

Of course, you may be leery of studies that come from the same country that gave us The Squid Game.

Monotherapeutically Yours,



10 thoughts on “Aspirin: How Low Can You Go?”

  1. What are your thoughts on Valazore aspirin formulation? I have found it helpful in terms of eliminating gastric side effects.

    • Angie,
      I looked at Valazore when a reader asked about it previously. Started to gather information for a post but never got to it.
      I was surprised that it has good data supporting that it has lower risk of gastritis/ulcers so it is reasonable for someone who has had gastric irritations with aspirin or otherwise and still needs aspirin if they can afford it.
      Dr P

  2. How about the aspirin studies that show how a single 80mg dose has excellent efficacy over 2-3 days? This is what I currently follow and approved by my cardiologist for secondary prevention. Also I take pycnogenol which has rct showing it also can provide the same benefits of aspirin but without the bleeding and clotting issues

  3. I have been on both Xarelto, a blood thinner, and aspirin long term. Have had microhematuria, invisible blood in the urine, also long term. Had a negative workup for the hematuria and was told blood thinners would not cause this, but who knows?

  4. I take both Xarelto, a blood thinner, and aspirin daily. And have had microhematuria, invisible blood in the urine, for years. Had a full workup for this, revealing nothing, and was told blood thinners would not cause it. Although who knows?

    • Mouldy hay in Holland caused in 1948 death in cows from bleeding. The active ingredient in the mouldy hay was developed into warfarin, the first anticoagulant for people, and for rat poison.

      Mould products like aflatoxin are a concern in many vegetarian foods and spices.

  5. Regarding bleeding from aspirin, here are two thoughts for consideration,

    Iron Deficiency Without Amemia is a serious condition whereby iron levels are dangerously low, yet the common blood tests for anemia remain within normal limits. Low ferritin levels confirm the diagnosis. Including ferritin in the usual blood tests is simple and economical, so if severe fatigue is a symptom, including ferritin in the blood tests might be considered.

    Aliquis is a blood thinner prescribed for many condition, including leg and lung clots. There are many other types and brands, including aspirin. The mode of action can vary, but all can have the same side effect.There is an increased risk of bleeding, especially from the bowel and kidney.

    Bleeding from lungs is not common in people, but common in animals poisoned with rat poison. Rat poison is also a powerful anticoagulant, and death in the rat is by uncontrollable bleeding.

    A simple test on bowel motions can reveal blood from the bowel. A simple urine stick test can show whether there is blood in the urine. Neither test is completely 100% reliable, with false negatives possible. A positive result indicates more thorough investigation.

    It may be worthwhile for patients on blood thinners, regardless of the type, to check to see if there is blood in their bowel motions or urine. The dipsticks for urine are readily available. The quality and reliability of these tests is not uniform so doing some homework on reliable brands is worth considering.


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