Key takeaways
- Blended CAC is total acquisition spend divided by total new patients, across every channel.
- Channel-reported CAC double-counts, because several platforms claim the same conversion.
- Blended CAC is the only version that reconciles with money actually leaving your account.
- Pair it with contribution margin to get payback period, which is the real growth constraint.
- Track it by category, because a blended-across-verticals number describes nothing you operate.
Why channel-reported CAC inflates
Every ad platform attributes conversions using its own model and its own lookback window. A patient who saw a Meta ad, searched your brand on Google, and converted from an email will frequently be claimed by all three.
Sum the platform-reported acquisitions and you get more patients than you actually acquired. Divide spend by that inflated number and every channel looks efficient at once, which is how a business with poor blended economics can have an entirely green dashboard.
The calculation
Total acquisition spend divided by total new patients acquired, for the same period. Spend means everything: media, creative production, agency fees, affiliate and influencer payments, and any acquisition-attributable tooling.
The number is usually higher than any individual channel report, and it is the number that reconciles with your bank statement, which is what makes it trustworthy.
Use it against contribution, not revenue
Blended CAC is only half of the pair. Divide it by contribution margin per patient per month and you get payback period in months.
That single number tells you how fast capital recycles, which for most operators is the actual constraint on growth rate. It also resists self-deception better than a ratio, because it depends on near-term cash rather than on a retention assumption stretching years out.
Segment by category, never blend across verticals
A portfolio operator computing one blended CAC across weight management, hair loss and sexual health gets a number that describes none of them.
Those categories have different price points, different contribution margins, different retention curves and different competitive acquisition costs. Blending them produces an average that will systematically overfund the weak one and underfund the strong one.
What to do with the number
Set a payback target rather than a CAC target. A CAC target is arbitrary; a payback target is a statement about how fast you need capital back.
- Compute contribution margin per patient per month, per category.
- Compute blended CAC per category from total spend and total new patients.
- Divide to get payback in months.
- Set the maximum acceptable payback based on your capital position, not on a benchmark.
- Then work backwards to a maximum blended CAC per category, and manage channels against that.
A fee structure that raises your affordable CAC as you grow
Because PharmaBro's transaction fee falls from 3% to 1.5% and there is zero revenue share and zero medication markup, contribution margin per patient improves with volume.
Higher contribution means a higher affordable CAC at exactly the point you want to bid harder. Under a percentage model that number is fixed by construction.
Conclusion
Channel-reported CAC is a useful directional signal and a poor decision input, because attribution ensures every channel claims credit it partly shares.
Blended CAC divided into contribution margin gives payback period, per category. That is the number to manage the business on, because it is the one that matches the money.
Frequently asked questions
What is blended CAC?
Total acquisition spend across every channel divided by total new patients acquired in the same period, including media, creative, agency fees and affiliate payments. It is the version that reconciles with your bank statement.
Why is channel-reported CAC misleading?
Because attribution models overlap. A single patient who touched three channels can be claimed by all three, which inflates total reported acquisitions and makes every channel appear efficient simultaneously.
What payback period should I target?
It depends on your capital position rather than on a benchmark. The point of computing it is that it converts an abstract efficiency question into a concrete one: how many times a year can you recycle acquisition capital?
Tobias LundHead of Growth
Came from performance marketing on the brand side. Now spends his time explaining why blended CAC is the only acquisition number that does not lie to you.