Grapefruit juice.and dosing

So I see that some people dose using GFJ to (I guess) save on cost as the GFJ increases the affect so you can use less rapamycin. My question is how do you determine what dose to use when using GFJ? I normally dose 8mg/week. I am about to restart as I stopped for 2 invasive medical procedures and was wondering what I should dose at if using GFJ. 2 mg? 3? to achieve 8mg dose w/o GFJ.

and how much GFJ should you take? (I will be using juice). any suggestions? and yes, I know it will not be medical advice.


I use 3 or 4 with GFJ every 2 weeks. 3 seems to be a little low, no problems. 4 gives me higher fasting glucose and higher LDL.

Weekly I’d try 2.

If you have not reviewed it yet, definitely read this thread Improve Bioavailability of Rapamycin (2)

Also there have been many discussions on this in addition to that thread. You may want to search on grapefruit in the search icon at top of page.

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ok. thx I have glanced at some comments but I really haven’t come across what I’m looking for (yet). i.e. if I want to obtain the level of 8mg/wk w/o using GFJ; how many mg should I try with GFJ and how much GFJ does one need to drink?

I’ll go to that link now and see what I find there.

A normal grapefruit (I take two), 1-4 hours before taking Rapamycin will increase the effect by 3-3.5X. So, if you’re targeting 8 mg/wk, you’d need to take 2-3 mg/week with GFJ.

2 mg + GFJ = 6-7 mg equivalent
3 mg + GFJ = 9-10.5 mg equivalent

So, it will probably be difficult to hit your 8 mg target. You’ll either be a little below or above it. Of course, this is all an estimate, so your biology will probably affect it as well.

Splitting a Rapamycin tablet is not suggested because when you break the coating, the pill becomes next to useless and loses 90%+ of its effectiveness.


The short answer is you really need to take a blood test, preferaby 48 hours after taking rapamycin, both without GFJ and with GFJ and compare the levels you get. Without doing that you really have no idea how much you need to get similar to 8 mg weekly without GFJ. The 3-3.5x increase in bioavailability with GFJ is just averages but the multiplier can be anything from 0 to over 8x depending on your genes, your source of GFJ, your dose of GFJ and other factors.


I would have to repectfully disagree. I need to start somewhere with GFJ. I can’t be spending money on special labs willy-nilly. I was looking for an avg of what people who are dosing with GFJ to give me a starting point.

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I take my rapamycin with Florida Ruby Red grapefruit juice, which I think tastes great.

I am not a fan of whole grapefruits.

The multiplication I get from drinking 10 oz an hour before I take rapamycin is approximately 3 ½ times.

How do I know this? Because of experimenting with doses for over 2 ½ years, I found out that 20 mg of rapamycin causes me to have diarrhea the second day after dosing. I have verified this more than once.

5 mg of Rapa + GFJ give me no diarrhea. At a 3.5 multiplier, this equates to about 17.5 mg equivalent.

6 mg of Rapa + GFJ gives me diarrhea. At a 3.5 multiplier, this equates to about 21 mg.

5 mg plus GFJ is the sweet spot for me.

I use this brand which is available in many Western grocery stores.

It seems consistent in taste and effect. This may be because the grapefruit is sourced from a variety of Florida farms. Whole grapefruit on the other hand is single sourced and you don’t know if you are getting the same effectiveness because the single source may change.


Thank you. this is the kind of info. I am looking for. Our local stores here in the South carry that as I have seen it in the larger grocery stores, although I normally don’t drink GFJ.

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P.S. how often do you dose using the 5mg & GFJ?

Typically I use a fresh squeeze red grapefruit - 5 fluid ounces with my 4 mg of zydus/rapamycin. Getting an 18.9 ng/mL after 2 hours.

However, in the past, I have used Simply Grapefruit juice from the store and have gotten the same results about a 3.5 to 6 increase.

So I know Simply even though it’s pasteurized, does work.


how often do you dose?

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Take my rapamycin… about every 7 to 9 days.

Sure if you don’t want to spend money on blood tests then you can just take something like 2 mg with GFJ and hope you’re getting the equivalent of 6-7 mg, but you would be taking the risk that you might be getting the equivalent of just 2-3 mg and not getting much benefits. If you’re willing to take that risk, that’s your choice. I’m willing to bet that a lot of people here that don’t take blood tests and take rapamycin with GFJ are getting much less rapamycin in their blood than they think.


Another thing I should add is that, for those of you that take rapamycin with GFJ and have access to a blood test but don’t want to take blood tests for rapamycin because of the cost, note that the cost of the blood test pales in comparison to the financial cost of not getting an effective increase in concentration, or the cost to your health of thinking you’re getting a lot more than you are. Blood tests for rapamycin levels are IMO a no brainer for anyone taking rapanycin that has access to such tests. We’re not talking about some random supplement, for which the dose doesn’t matter so much in the long run. We’re talking about what is most likely the most powerful anti-aging supplement/drug that exists now. So of all the supplement/drugs people take for longevity, rapamycin is probably the most important to get right. So it makes sense to invest more time and money into getting it right.


“Sure if you don’t want to spend money on blood tests”

you are reading into my post what you want to see, not what I said. that’s not very objective of you nor is it correct.

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That’s not true. I’m not reading what I want to see. I’m reading what you said. You literally said: “I can’t be spending money on special labs”. So I naturally took that to mean you are not in a good position to be spending money on blood tests. If that’s not what you meant then I am curious to know why you don’t want to take a blood test for rapamycin?

As far as me reading what I want to see. I am absolutely not doing that. Why would I want you to not take blood tests because they are expensive? Quite on the contrary I wish you and everyone else on here could afford to take blood tests because it would be beneficial for you (and for the rest of us if you share the results of your test).

You forgot to quote the part where I said willy-nilly which is important to my statement. I also said I needed to start somewhere; r.e. with GFJ. I need a point to start from and zero GFJ is not it. lets not get in a tit for tat conversation and just leave it at that.


I picked that GFJ up today at my local wallyworld. (Simply) They didn’t have the FL Natural Ruby red although I’m sure I’ve seen it there before.


I see. Yeah I didn’t understand what you meant by the willy-nilly part so that could be it. Although my English is good I’m not a native English speaker. Anyways, just a friendly tip, some studies showed that 200 ml of GFJ was not enough to increase concentrations of drugs significantly and that many people would need more than that for significant effects, so it’s not a bad idea to drink 300-400 ml to increase the chances of getting a strong increase in bioavailability. Good luck!