Bitcoin (BTC) price action may be “unsustainably high,” as one metric hits its highest levels in seven months.

Data from on-chain analytics firm Glassnode confirms that on Dec. 21, Bitcoin’s network value to transaction (NVT) signal reached levels not seen since April.

Bitcoin activity may not support $17,000 BTC price

Created by statistician Willy Woo, NVT essentially measures the ratio between on-chain activity and the price of Bitcoin.

NVT signal modifies its readings by using a 90-day moving average of daily transaction volume instead of raw data, something Glassnode says “improves” NVT and allows it “to better function as a leading indicator.”

On Dec. 21, the NVT signal hit 18.58, a level that last appeared as Bitcoin declined in the final days of April. At the time, BTC/USD traded at just over $40,000.