SiPhox vs Function Health: home arm draw or a yearly lab membership?

SiPhox vs Function Health: the short answer

Function Health wins on value; SiPhox wins on convenience and frequency. Function charges $365 a year for 160+ lab tests across two venous draws at a Quest lab (about 100 at the first visit and 60 at a follow-up 3 to 6 months later), which works out to about $2.28 per result. SiPhox charges $124 plus $25 shipping per test ($149) for 31 biomarkers on its default Longevity Essentials panel, about $4.81 per result, but you draw the blood yourself on your upper arm with no needle and can repeat it every month, quarter or six months.

If you want one deep annual snapshot and do not mind a lab visit, Function is the better buy. If you hate needles, cannot get to a Quest lab easily, or want to watch ApoB, HbA1c or testosterone move every quarter, SiPhox is the only one of the two that does it. Prices below were read on both companies' sites on September 29, 2026.

Want to test at home instead?SiPhox Longevity Essentials: 31 biomarkers including ApoB, Lp(a) and hs-CRP from an upper-arm draw. $124 a test plus $25 shipping.

See SiPhox plans

Side by side

Two corrections to the table from our September 29, 2026 check: Function says it covers 48 states and does not yet serve Rhode Island or Hawaii, and its pricing page lists an at-home draw by a licensed specialist without a separate published fee. Function's FAQ says the first results arrive within 48 hours of the draw, with the rest following as the lab finishes them.

Yearly cost and cost per biomarker

Function has one price: $365 a year, charged up front, for two draws. SiPhox is billed per test, so the yearly cost depends on how often you test. "Results" below counts every biomarker result you receive in a year, so a marker tested twice counts twice.

SiPhox's year-one figures use the $99 first-test price it advertises for new members; renewals are $124 plus $25 shipping. The last row is a real option for some people: Function's full panel once a year, plus two SiPhox Longevity kits at the in-between quarters, gets you ApoB three times a year for $663. Function alone tests ApoB once a year. Run your own cadence in the cost per biomarker calculator, and see every SiPhox price in our SiPhox cost guide.

Both are HSA and FSA eligible. Function does not offer refunds for past payments; SiPhox does not refund a test once the kit ships.

Worked example: a year of ApoB tracking

The right choice depends on how many times a year you need the one or two markers you actually care about. Three hypothetical readers, priced with the figures read on both sites on September 29, 2026:

The rule of thumb: at one or two checks a year, Function's price per result wins by a wide margin. At three or more checks of the same marker, SiPhox's per-test pricing wins, because Function only repeats about 60 of its markers at the follow-up and never repeats ApoB, Lp(a), thyroid or hormones within the year. Plug your own cadence into the cost calculator.

Biomarker overlap

Function tests far more. Its list includes things SiPhox does not measure at all: fasting insulin, homocysteine, an omega-3 index, a full blood count, lead and mercury, urinalysis, ANA and a PSA with free PSA for men. Function also lists LDL particle number and size, which SiPhox does not offer.

SiPhox's advantage is not breadth, it is repetition. Function's own list marks which markers are "tested twice a year": the basic lipid panel, hs-CRP, glucose, HbA1c, insulin, kidney and liver chemistry, the blood count and urinalysis. ApoB, Lp(a), thyroid, hormones, ferritin and vitamin D appear once a year. SiPhox puts ApoB, Lp(a), hs-CRP, HbA1c, testosterone, SHBG, DHEA-S, vitamin D and ferritin on every Longevity Essentials test, and you can switch to the Thyroid, Hormone or Heart & Metabolic panel on any cycle.

Function data: "what we test" page, September 29, 2026. SiPhox panels: SiPhox panel pages, same day. "Not listed" means the marker does not appear on Function's list. SiPhox measures C-peptide instead of fasting insulin, which Function does not list.

Collection and convenience

Function: a venous draw by a phlebotomist at one of 2,000+ Quest locations, or at home or work by a licensed specialist in the areas Function covers. Your arm, a needle, a few tubes, and a fasting appointment slot. Twice a year.

SiPhox: a kit by mail. You warm your arm, stick the EasyDraw device on the outside of your upper arm, press a button and let it fill for up to 5 minutes, then ship it cold and overnight from a staffed FedEx location, Monday to Thursday. A live coach can walk you through it on video. Larger panels need more than one device, and every device in the kit must be used. Our EasyDraw guide covers how to avoid a failed draw.

The trade-off is sample type. Function's venous blood is the clinical standard. SiPhox uses capillary blood from the arm; it reports a 95% to 99% correlation with venous results from its own in-house comparisons, and it has not published a peer-reviewed study of the device. Independent research on a similar upper-arm device found 17 of 19 common chemistry tests within accuracy limits.

Turnaround and clinician access

• Function: first results within 48 hours of your draw, according to its FAQ, with the rest arriving as they finish. Clinicians review every result and flag issues, and you get a written summary and a personalized protocol. Add-ons include an annual MRI at $999 and a multi-cancer test.
• SiPhox: results 7 to 10 days after the lab receives the sample, and some customers report 14 days or more. No clinician reviews your results by default: SiPhox describes itself as a wellness service. A results review with a health expert is $50 per test.

If a doctor reading your numbers is important to you, Function wins this section clearly. With SiPhox, plan to take anything unusual to your own doctor and confirm it with a standard lab test.

From order to results: the real timeline

Function Health: you join, book a fasting morning slot at a Quest location (or a home visit where offered), have the draw, and see first results within about 48 hours, per Function's FAQ. The follow-up draw comes 3 to 6 months later. The slowest step is usually finding an appointment that suits you.

SiPhox: the kit ships within about 3 days and arrives 3 to 5 days later. You draw and ship on the same day by FedEx overnight, Monday to Thursday only, and the lab takes 7 to 10 days from receipt. Added up, a first SiPhox result takes roughly 2 to 3 weeks from the day you order (our arithmetic from SiPhox's stated shipping and lab times). Some one-star reviewers report 14 to 28 days after shipping.

If speed matters because you want a number before a doctor's visit, Function (or any lab draw) is the faster route. For routine quarterly tracking, the SiPhox wait rarely matters as long as you ship early in the week so the sample is not stuck in transit over a weekend.

Where you can use them

Function only says New York and New Jersey "can cost more". One independent review reports membership there at $600 or more a year, which would put it above SiPhox quarterly in New Jersey ($571 in year one). Check the price for your ZIP code at checkout.

What customers complain about

Function Health had a 4.5 out of 5 Trustpilot score from 2,990 reviews on September 29, 2026 (74% five-star, 6% one-star). Recent one- and two-star reviews mostly concern slow, automated support, paid add-on tests that went missing or were never run, and gift memberships that the buyer cannot manage.

SiPhox Health had 4.7 from about 950 reviews (84% five-star, 8% one-star). In the 20 most recent one-star reviews the themes were support that is hard to reach (9), results slower than quoted (8), billing and renewal disputes (6), a device that did not collect enough blood (6) and redraws (5). The full SiPhox review covers each one.

Which one to choose

Still deciding between the lab memberships? Read Function Health vs Superpower or our ranking of the best at-home blood tests.

Test ApoB at home, every quarterPick Longevity Essentials, Heart & Metabolic, Thyroid or Hormone and switch any cycle. HSA and FSA cards accepted.

Check SiPhox price

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