comparisons
Published by Floriva · Updated 2026-03-21 · How Floriva checks its guides
Glow vs Natural Cycles: Data Monetization vs FDA Clearance
Natural Cycles is FDA-cleared birth control. Glow sold user data to insurers and advertisers. Here's how they compare on privacy and cost.
Glow is a venture-backed fertility and cycle tracker with a documented history of data sharing. Natural Cycles is an FDA-cleared contraceptive app built around basal body temperature. They serve different purposes, but both require accounts and store data server-side.
Different tools, competing for the same user
Glow and Natural Cycles both appear in searches for "fertility tracking app," but they are built for different things.
Glow is a cycle and wellness tracker with partner-sharing features and fertility calendars. Its revenue model involves data monetization. The company has documented relationships with insurers and third-party advertisers who receive health data. The free tier exists because the data has commercial value.
Natural Cycles is an FDA De Novo cleared contraceptive device that uses basal body temperature to determine fertile and non-fertile days. The subscription funds the product. There is no advertising model and no documented enforcement actions for data misuse.
The comparison matters if you need general cycle tracking and are deciding whether the data risks of either app are worth it. For contraception, Natural Cycles has regulatory backing. Glow does not.
The data risk gap
Both apps require accounts. Both store data server-side. Neither offers on-device architecture.
Glow's data risk differs from Natural Cycles' in kind. Glow's business involves monetizing health data commercially. Insurers and advertisers receive information derived from your fertility and cycle logs. That is a form of data exposure separate from law enforcement access, and users have no mechanism to opt out.
Natural Cycles operates under GDPR and has no documented commercial data-sharing problems. Its server-side exposure is primarily legal: a court order can compel production of user data. That risk applies to all server-based period trackers.
In states with abortion restrictions, both apps create records that can be subpoenaed. A prosecutor with a valid court order can compel either company to produce user data. A company holding no data cannot produce any.
Temperature tracking: what Natural Cycles actually requires
Natural Cycles requires active daily participation. You measure basal body temperature every morning before getting out of bed, using a specific thermometer accurate to two decimal places. The algorithm uses that data to predict fertile windows.
Glow lets you log data when convenient. Natural Cycles does not. Natural Cycles' effectiveness depends on consistent measurement. Missed readings reduce accuracy. The app is not appropriate for users who want hands-off tracking.
Floriva supports daily logging and pattern review. Check current app onboarding for exact fertility fields before you rely on a specific BBT workflow.
Cost breakdown
Natural Cycles is listed at $12.99/mo or $99.99/yr (as of original publication; check current rates at naturalcycles.com). Glow has a free tier and a premium at $59.99/yr. Floriva is a paid app with no free tier; plans are shown in the app. If FDA-cleared contraception is the use case, Natural Cycles' price premium is specific to that regulatory value. If cycle tracking is the use case, Floriva stores nothing on a server.
Cited signals
- Glow Premium costs $59.99/yr, the free tier is ad-supported Glow app pricing
- Flo Health paid a $59.5M combined settlement for sharing reproductive health data without user consent Reuters / FTC, September 2025
Glow vs Natural Cycles vs Floriva: Features and Privacy
| Feature | Floriva | Glow | Natural Cycles |
|---|---|---|---|
| FDA-cleared contraception | No | No | Yes (De Novo 2018) |
| Temperature tracking | Yes | Optional | Required |
| On-device storage | Yes | No | No |
| Account required | No | Yes | Yes |
| Data monetization history | No | Yes | No documented |
| Data can be subpoenaed | No | Yes | Yes |
| Price | Paid app (no free tier) | Free / $59.99/yr | $12.99/mo |
Strengths and trade-offs
Floriva
Pros
- On-device storage, nothing on servers to subpoena
- No account required
- Paid subscription for all users, no free tier
- Temperature tracking available
Cons
- Not FDA-cleared for contraception
- Smaller feature set than established apps
Glow
Pros
- Free tier with solid cycle and fertility prediction
- Community and partner-sharing features
- Detailed logging for fertility treatment cycles
Cons
- Business model depends on health data monetization
- Data shared with insurers and third-party advertisers
- Server-based, data accessible via legal process
- No on-device architecture option
Natural Cycles
Pros
- FDA De Novo cleared for contraception
- Algorithm built on peer-reviewed fertility research
- No documented advertising data sharing
Cons
- Requires daily basal body temperature, passive tracking not possible
- Most expensive period tracker in this comparison
- Server-based, data accessible via legal process
- Effectiveness depends on consistent measurement behavior
Quick answers to the obvious questions.
Is Glow period tracker safe to use
Glow has documented data-sharing practices with insurers and third parties as part of its business model. It stores data server-side, which means the data exists on Glow's servers and is accessible to law enforcement via subpoena. For users in states with abortion restrictions, this is a real risk. Glow's free model is subsidized by data monetization. Health data is part of the revenue stream.
Is Natural Cycles FDA approved
Natural Cycles received FDA De Novo clearance in 2018 as a contraceptive app, the first digital contraceptive to receive this designation in the US. De Novo clearance means the FDA reviewed clinical evidence and found the device safe and effective for its intended use. This is meaningful regulatory oversight, but the clearance is for contraceptive efficacy, not data privacy.
Does Natural Cycles sell data
Natural Cycles has not faced FTC enforcement actions for data sharing the way Flo and Premom have. The company is Sweden-based and operates under GDPR, which restricts commercial data sharing more aggressively than US law. That said, Natural Cycles does require an account and stores data server-side. Data exists on their servers and is theoretically accessible via court order.
Which is better for fertility tracking, Glow or Natural Cycles
For FDA-cleared fertility awareness as a contraceptive method, Natural Cycles is the only option in this comparison. Its temperature-based algorithm has been clinically studied. Glow covers fertility calendars and ovulation prediction but is not regulated for contraceptive use. If privacy during fertility tracking matters, neither app has on-device architecture. Floriva does.
Questions people ask before they switch.
Can I use Glow without sharing my data?
Glow requires an account and stores data server-side. The app's business model involves data monetization. You cannot opt out of server-side storage while using Glow. The data architecture is not configurable by users. Deleting your Glow account submits a deletion request for server-side data, but data already shared with third-party partners may remain with those companies.
How effective is Natural Cycles as birth control?
Natural Cycles reports 93% effectiveness with typical use and 98% with perfect use in published clinical data. These rates are lower than hormonal contraception (99%+) but comparable to barrier methods with typical use. Effectiveness depends heavily on consistent daily temperature measurement and following the app's guidance on red and green days.
What is the difference between Glow and Natural Cycles?
Glow is a general wellness and fertility tracking app with a free tier subsidized by data monetization. Natural Cycles is an FDA-cleared contraceptive device that requires daily temperature tracking and a paid subscription. They serve different use cases: Glow for general cycle awareness, Natural Cycles for fertility awareness-based contraception with regulatory backing.