SiPhox vs Rythm Health: two needle-free arm tests compared

SiPhox vs Rythm Health: the short answer

These are the two closest rivals in home blood testing: both use an upper-arm device instead of a finger prick or a needle, both are subscriptions, both test ApoB and hs-CRP. Rythm Health (often searched as "Rhythm") is cheaper and quicker: $79 a test plus shipping and tax, about $100 all-in according to one independent review, with results in about 48 hours once the lab starts. SiPhox Health is $124 plus $25 shipping ($149) per test with results in 7 to 10 days.

What the extra money buys with SiPhox is coverage. Rythm has no Lp(a), no HbA1c (it uses fructosamine), no DHEA-S, LH, FSH, PSA or thyroid antibodies, and one fixed panel per sex. SiPhox has four switchable panels, including a full thyroid panel and a hormone panel, plus Ultimate 360 with 62 markers. Prices were read on both sites on September 29, 2026.

Need Lp(a), HbA1c or thyroid antibodies?SiPhox covers them across four switchable panels, collected on the upper arm at home. $124 a test plus $25 shipping.

See SiPhox plans

Side by side

Updates from our September 29, 2026 check: Rythm says it is available in all 50 states and HSA and FSA eligible, and that every result is reviewed and signed off by a state-licensed physician before release. It does not include a consultation.

Rythm Health review: what you get

Rythm sells one product: a monthly home blood test. The subscription renews every 30 days at $79 plus shipping and tax; on September 29, 2026 the first test was advertised at 25% off ($59.25). You can skip for up to 90 days, so testing roughly every quarter is possible. Crown Counseling's June 2026 review reports that the kit uses the Tasso+ upper-arm device and that the kit and two-way shipping bring a regular order to about $100.

• Panel: "25+ biomarkers". Its list shows 27 for men and 28 for women: ApoB, LDL, HDL, total cholesterol, remnant cholesterol, triglycerides, hs-CRP, fructosamine, albumin, uric acid, vitamin D, ferritin, creatinine, eGFR, ALP, GGT, testosterone (total and free), estradiol, SHBG, cortisol, TSH, plus free T3, free T4 and progesterone for women and hemoglobin and hematocrit for men.
• Speed: kits arrive in about 2 to 4 days. Results within 48 hours once processing starts, or within 3 business days of the lab receiving the sample, per Rythm's FAQ.
• Guarantee: a 90-day money-back guarantee on your first purchase only, if you complete the test and ask within 7 days of getting results.
• Reputation: 4.8 out of 5 on Trustpilot from 2,984 reviews on September 29, 2026 (87% five-star, 3% one-star), the best score of any service we cover.
• Add-ons: none yet; Rythm says they are on its roadmap.

Our take: Rythm is a strong, well-reviewed product for monthly tracking of lipids, testosterone and a few metabolic markers. It is narrower than SiPhox, and the gaps (Lp(a), HbA1c, thyroid antibodies) are the markers many people buy a longevity panel for.

Yearly cost and cost per biomarker

Rythm is cheaper per result. The last row shows the SiPhox case for the extra cost: rotate Longevity, Heart & Metabolic, Thyroid and Hormone over a year and you see about 56 different markers (some are sex-specific), against Rythm's 27 or 28 repeated each time. SiPhox's year-one figure uses its $99 first test. More in our SiPhox cost guide and the calculator.

The gap is about $171 a year at a quarterly cadence ($196 from year two, when SiPhox is $596) and about $563 a year if you test monthly. Rythm's first test was also advertised at 25% off ($59.25 before shipping) on September 29, 2026, which narrows year one further in Rythm's favor.

Biomarker overlap

Rythm has a few markers SiPhox's core panels lack: uric acid, remnant cholesterol, fructosamine, and kidney and liver markers (creatinine, eGFR, ALP, GGT) on every test. SiPhox's Longevity panel has no kidney or liver markers; its Heart & Metabolic panel does.

Worked examples: who each one suits

Because the two use the same kind of device, the choice comes down to which markers you need and how often. Three hypothetical readers, priced with figures read on September 29, 2026:

Collection and convenience

Both are upper-arm capillary devices, and both ask for a warm arm and overnight FedEx return. The practical differences:

• Returns: Rythm lets you schedule a free FedEx pickup from your dashboard and allows weekend returns; SiPhox requires a same-day drop at a staffed FedEx location, Monday to Thursday, with a cold pack.
• Fasting: Rythm asks for a fasted, first-thing-in-the-morning collection.
• Help: SiPhox offers a live video coach for the draw; Rythm offers text and chat support.
• Kit life: Rythm says its kits do not expire, but asks you to return a sample within 7 days of receiving the kit.

See our EasyDraw guide for SiPhox's steps.

How accurate are upper-arm devices?

Neither company has published a peer-reviewed validation of its own kit. Rythm says each biomarker uses the same sample volume as a venous test and that its lab is CLIA-certified and CAP-accredited. SiPhox says its tests correlate 95% to 99% with venous draws in its own quarterly comparisons against Labcorp and Quest. The best independent evidence is a 2025 study of Labcorp's similar upper-arm vacuum device: it collected about 538 microliters on average and 17 of 19 common chemistry tests met CLIA accuracy limits, with glucose and potassium biased. That is one reason both services avoid glucose (SiPhox uses HbA1c, Rythm uses fructosamine). Treat results from either as good for trends and confirm anything surprising with a venous test through your doctor.

Turnaround and clinician access

Rythm is clearly faster: about 2 to 3 business days after the lab receives your sample, against 7 to 10 days for SiPhox. Rythm results are signed off by a state-licensed physician, and both give you an AI coach. Neither includes a consultation; SiPhox sells a $50 results review. Take results that worry you to your own doctor.

What customers complain about

Rythm: few negative reviews. The ones there mention biomarkers missing from results, marks on the skin after the draw, and resolutions that felt too small. Rythm's FAQ also says a sample can look full and still be rejected for too little plasma.

SiPhox: 4.7 from about 950 Trustpilot reviews, with one-star themes of slow support, results slower than quoted, renewal disputes and short draws needing a redraw. Rythm's reviews are stronger on support.

Which one to choose

Also read our full SiPhox review and the best at-home blood tests ranking.

Broader panels, same needle-free drawLongevity, Heart & Metabolic, Thyroid and Hormone included; switch each cycle. HSA and FSA accepted.

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