Your LTV goes up when your collateral's price falls or interest is added. A higher LTV means a higher interest rate and brings you closer to liquidation.
How You'll Know
Your Credit Line shows your current LTV. When it comes within 10 percentage points of your Liquidation LTV, your Credit Line shows Liquidation Risk, and we try to warn you by email and push notification. For example, if your Liquidation LTV is 90%, this starts at 80%.
How to Lower Your LTV
Add collateral. Open your Credit Line and tap Add Collateral. See How do I add or remove collateral?
Repay part of what you owe. Open your Credit Line, tap Repay, and choose Repay from Wallet or Repay with Collateral.
Say you owe $8,000 against $10,000 of BTC, so your LTV is 80%. Adding $2,000 of collateral brings it to about 67%. Repaying $2,000 from your Wallet brings it to 60%. Repaying with collateral lowers it less, because your collateral goes down too.
Act Early
Prices can move fast, and you can't add collateral or repay once liquidation has started. If your LTV reaches your Liquidation LTV, your Credit Line is closed and all of your collateral is sold to repay what you owe. See How does liquidation work?