By the time you hit your forties, a small but stubborn fraction of your cells have stopped dividing — not because they died, but because they refused to. They sit there, metabolically active, leaking inflammatory signals into the tissue around them. Researchers call them senescent cells. The popular press calls them zombie cells. Either way, clearing them out is one of the most promising leverage points in modern aging biology — and the class of compounds that does the clearing is called senolytics. This is the practical guide we wish existed when we started.
The 30-second answer
- Senolytic = clears senescent cells. A different mechanism from antioxidants, NAD+ boosters, or anti-inflammatories.
- Three flavonoids have the strongest senolytic data: Fisetin (the most potent in mouse screens), Quercetin (paired with Dasatinib in the original D+Q trials), and Apigenin (works upstream by inhibiting CD38, the enzyme that degrades NAD+).
- Senolytics are pulse-dosed, not daily. The published mouse and human protocols use 2–3 days a month, not continuous use. This matches the biology — senescent cells accumulate slowly, so you only need to clear them periodically.
- Stack pairs well with NMN/NAD+. Apigenin in particular raises NAD+ availability by blocking the enzyme that breaks it down.
What is a senescent cell, actually?
Cells have a finite number of divisions. When DNA damage, oxidative stress, or telomere shortening pushes a cell past a threshold, it has three options: repair, die by apoptosis, or stop dividing. The third option is senescence. The cell stays metabolically active but exits the cell cycle permanently, resistant to the normal apoptosis signals that would otherwise clear it.
For most of life that's fine — senescence is actually a tumor-suppressor mechanism, since a cell that won't divide can't become cancer. The problem is that senescent cells secrete a cocktail of inflammatory cytokines, growth factors, and proteases known as the senescence-associated secretory phenotype (SASP). The SASP is the active ingredient. It drives chronic low-grade inflammation in surrounding tissue — sometimes called "inflammaging" — and is implicated in osteoarthritis, frailty, kidney decline, type 2 diabetes, atherosclerosis, and pulmonary fibrosis. A senescent cell isn't dangerous because it stopped dividing. It's dangerous because of what it leaks.
The senolytic hypothesis is straightforward: if you can selectively kill the senescent cells without harming normal cells, the SASP goes away with them, and the tissue around them recovers.
The evidence this actually works
The landmark paper is Zhu et al. 2015 in Aging Cell, which screened a library of compounds for the ability to selectively kill senescent cells in culture and in mice. The two hits that emerged were the cancer drug Dasatinib and the dietary flavonoid Quercetin — together known as D+Q. In aged mice, D+Q improved cardiac function, exercise capacity, and frailty markers. Subsequent work (Yousefzadeh et al. 2018, EBioMedicine) screened ten flavonoids head-to-head and found Fisetin to be the most potent natural senolytic, extending median lifespan in already-aged mice when started at 85 weeks of age.
Human translation has begun. Hickson et al. 2019 (EBioMedicine) ran the first open-label senolytic trial in humans — D+Q in patients with diabetic kidney disease — and found that three days of dosing reduced senescent cell markers in adipose tissue and skin biopsies for at least eleven days after the last dose. Justice et al. 2019 (EBioMedicine) ran the same regimen in idiopathic pulmonary fibrosis and saw improvements in physical function. The Mayo Clinic is currently running multiple Fisetin trials (NCT03675724 and others) in conditions ranging from frailty to long COVID.
Two important caveats. First: the human evidence is early and most trials are small. Second: the doses used in the published mouse work are higher than what you can hit with diet alone. That gap is exactly what supplemental flavonoids are aimed at closing.
The three flavonoids worth taking seriously
Fisetin — the most potent natural senolytic in screening
Fisetin is the flavonoid that came out on top in the Yousefzadeh 2018 head-to-head screen. In aged mice it cleared senescent cells across multiple tissues and extended median and maximum lifespan when started in late life. It's found at very low concentrations in strawberries, apples, and onions — far below what the trials used. Mayo Clinic's ongoing Fisetin trials in humans use intermittent high doses (typically 20 mg/kg/day for two consecutive days, monthly), which is roughly what a 500 mg supplement provides for an average adult on a pulse-dose schedule.
Bioavailability is the catch with all flavonoids — fisetin in particular has poor oral absorption in standard form. Look for products that disclose dose clearly and consider taking with a fat-containing meal to improve uptake.
Our pick: Fisetin 500 mg — Senolytic Flavonoid for Cellular Cleanup. 60 capsules, 500 mg per capsule, designed for the standard 2-days-per-month senolytic pulse.
Quercetin — the original half of D+Q
Quercetin is the flavonoid half of the original Mayo Clinic D+Q senolytic combo. On its own at supplemental doses it has weaker single-agent senolytic activity than Fisetin, but it remains the most-studied flavonoid in human senolytic trials because it's the Q in every D+Q paper. It's also a strong natural antihistamine and mast-cell stabilizer (Mlcek et al. 2016, Molecules), which is why it shows up in allergy and immune protocols as well.
The practical case for Quercetin is that it's the flavonoid with the longest human safety record in senolytic dosing, and that it pairs synergistically with Fisetin — different binding affinities for the senescent-cell anti-apoptotic network, so combining them widens the net of which senescent cells you can clear.
Our pick: Quercetin 500 mg — Senolytic Flavonoid + Natural Antihistamine. 60 capsules, 500 mg per capsule.
Apigenin — the upstream CD38 inhibitor
Apigenin works on a different axis from Fisetin and Quercetin. It's a potent inhibitor of CD38, the enzyme that consumes NAD+ as a substrate (Escande et al. 2013, Diabetes). CD38 expression rises with age and is one of the main reasons NAD+ levels fall — every NAD+ molecule degraded by CD38 is one your sirtuins and PARPs can't use.
This makes Apigenin an unusually elegant pairing for anyone already taking NMN, NR, or Liposomal NAD+: instead of just adding more NAD+ precursor, you're plugging the leak that drains the NAD+ you already have. It's also a mild senolytic in its own right and has SASP-suppressing effects in senescent cells that aren't fully cleared (Perrott et al. 2017).
Apigenin is the only one of the three flavonoids on this list that arguably belongs in a daily protocol rather than a pulse-dose schedule, because the CD38-inhibition mechanism benefits from continuous suppression.
Our pick: Apigenin 50 mg — CD38 Inhibitor for NMN & NAD+ Stacks. 60 capsules. Designed specifically as a daily pairing for NAD+ precursor protocols.
How to actually take them
The published senolytic protocols are pulse-dose, not daily. The biological rationale: senescent cells accumulate slowly over months, so a brief high-dose pulse that clears them and then comes off is more efficient than a low daily dose. It also reduces any concern about hitting healthy cells unnecessarily.
- Standard senolytic pulse: Fisetin 500 mg + Quercetin 500 mg, taken together for 2 consecutive days per month, with a fat-containing meal.
- Stronger pulse (Mayo-style): the same combination for 3 consecutive days per month.
- Apigenin: 50 mg daily, ideally alongside your morning NMN or NAD+ dose.
- Spacing: at least 4 weeks between pulses. Senescent cells accumulate too slowly to benefit from more frequent clearing.
If you're stacking senolytics with the foundational NAD+ protocol, the order is: take Apigenin daily as part of your morning NMN routine, and then layer the Fisetin + Quercetin pulse on top once a month. The two strategies complement each other — Apigenin keeps NAD+ from being drained, the monthly pulse clears the senescent cells that are leaking SASP into your tissues.
Who shouldn't take senolytics (yet)
Senolytic flavonoids are generally well tolerated, but the senolytic mechanism is real enough that some caution is appropriate. Skip the pulse dose and consult your physician first if you are: pregnant or nursing, on chemotherapy or immunosuppressants, on blood thinners (Quercetin in particular has mild antiplatelet effects), or actively recovering from surgery. Apigenin at 50 mg/day is generally considered low-risk for daily use, but the same conditions apply.
Children and teenagers should not take senolytics. Cellular senescence plays a constructive role during development; clearing senescent cells is an old-tissue intervention.
The bottom line
Senolytics are a different class of intervention from antioxidants, NAD+ boosters, or general anti-inflammatories. They target the small population of cells that have stopped dividing but won't die — the source of inflammaging that drives a long list of age-related conditions — and the published evidence in mice and the early human trials is genuinely encouraging. Three flavonoids have the data to take seriously: Fisetin (the most potent in screening), Quercetin (the most-studied in human trials, paired with Fisetin), and Apigenin (the upstream CD38 inhibitor that pairs with NAD+ precursors). Pulse-dose Fisetin + Quercetin two days a month, take Apigenin daily alongside your NMN. Re-evaluate at three months.
Build your senolytic stack: Senolytics collection · Fisetin 500 mg · Quercetin 500 mg · Apigenin 50 mg.
Already on NMN? See our full longevity stacking protocol for how senolytics fit into a complete daily routine.
This article is for informational purposes only and is not medical advice. These statements have not been evaluated by the FDA. The supplements discussed are not intended to diagnose, treat, cure, or prevent any disease. Consult your physician before starting any supplement, especially if you have a medical condition or take prescription medication.