Altcoin spot volume has climbed to nearly four times Bitcoin's, Glassnode data shows — the highest ratio since September 2025. The same week, US spot Bitcoin ETFs drew in almost $2.4 billion across the five sessions ending Sept. 25. Sounds fine, until you look at the daily numbers.
The inflows fell every single day: $999.0 million on Sept. 21, then $714.7 million, $346.9 million, $190.7 million, and finally $134.5 million on Sept. 25. That last figure is 86.5% below where the week started.
The ETF bid faded fast
Glassnode's rolling weekly ETF inflow reading still sits near $2.7 billion, which it calls the largest inflow in almost a year. So the money hasn't left. It just stopped arriving at the same pace, and roughly 80% of combined Bitcoin and Ethereum ETF flows went to BTC products last week — Ethereum drew $602.8 million over the same five sessions.
Meanwhile, Wintermute's Sept. 28 OTC report describes net BTC selling on its desk, driven mainly by retail clients taking profits and rotating into altcoins. Wintermute's data says that in more than 80% of comparable cases, the weeks following this kind of stretched breadth were flat to negative — early-cycle periods excepted.
Breadth stretched across the board
It's not subtle. As of Sept. 23, 72.5% of altcoins tracked by Glassnode were outperforming Bitcoin, up from 39% during August's squeeze. 87% of Binance-listed altcoins were trading above their 200-day averages, versus roughly 20% in August. CryptoQuant contributor Darkfost found the altcoin market excluding Bitcoin has added about $371 billion, or 45%, since June.
Glassnode treats the altcoin/BTC volume ratio as a historical warning condition. Similar bursts of aggressive risk-taking have often coincided with local Bitcoin tops.
The rally itself looks mostly spot-driven, too. Altcoin perpetual open interest barely expanded over the prior 30 days, and fewer than half of tracked markets added positions.
Profit-taking on the Bitcoin side
The Bitcoin data backs up the rotation. Glassnode's Sept. 28 report shows spot cumulative volume delta down 86.5% to just $17.3 million. Perpetual futures delta sat at negative $261.5 million, with futures open interest holding at $38.9 billion.
Profit-taking is visible in the supply figures. The share of Bitcoin supply in profit rose to 74% from 69.3% a week earlier, and the realized profit-to-loss ratio jumped 79.6% to 1.4. Traders are converting gains into stablecoins and altcoins — stablecoin market cap sits near $306.4 billion, up 0.89% over 30 days, per DefiLlama.
Altcoin deposits to exchanges have reached their highest level since October 2025, with weekly averages above 22,700 deposit transactions on Binance, 8,300 on Coinbase, and 32,000 across other venues. That's often a precursor to selling.
Macro isn't helping
Wintermute names oil, rates, and the chance of another Fed hike as the main external threats to the current regime. It's not hard to see why. The Fed raised its policy rate range to 3.75%–4.00% on Sept. 16. The 10-year Treasury yield touched roughly 5.23% on Sept. 25 — its highest since 2007. Brent crude moved above $107 on Sept. 28.
The next test is whether ETF inflows stabilize or keep sliding when the new week's prints land. If the daily declines continue, the altcoin breadth trade will be running without the institutional bid that carried Bitcoin through the summer.
