How-to: Add collateral to a loan

Post additional cirBTC as collateral against an open loan. Adding collateral lowers the loan’s LTV and raises its health factor without changing the outstanding debt. This is the standard response to a margin call when you want to keep the loan open rather than repay it.

Prerequisites

Before you begin, ensure that you’ve:

Completed the Borrow USDC against cirBTC collateral quickstart and hold at least one loan in active status.
Held sufficient cirBTC in your Mint balance to cover the additional collateral you plan to post.

Steps

Submit the collateral request

Call POST /v1/borrow/loans/{id}/collateral with the amount of cirBTC you want to add in raw uint256 base units.

curl -X POST https://api-sandbox.circle.com/v1/borrow/loans/fc988ed5-c129-4f70-a064-e5beb7eb8e32/collateral \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "idempotencyKey": "e5c6d7b8-9012-4a3b-cdef-1234567890ab",
    "amount": "2500000"
  }'

The endpoint returns an onchainJob with jobType: add_collateral:

{
  "data": {
    "id": "f6a7b8c9-d012-3456-efab-456789012345",
    "jobType": "add_collateral",
    "status": "received",
    "createDate": "2026-06-25T10:15:00.000Z",
    "updateDate": "2026-06-25T10:15:00.000Z"
  }
}

Save the job id. You poll it in the next step.

Poll the job to completion

Circle builds, signs, and submits the onchain UserOperation for the added collateral. The job progresses through submitted and confirmed to completed. Poll GET /v1/borrow/jobs/{id} until you see the terminal state.

{
  "data": {
    "id": "f6a7b8c9-d012-3456-efab-456789012345",
    "jobType": "add_collateral",
    "status": "completed",
    "amount": "0.025",
    "asset": "CIRBTC",
    "collateralAmount": "0.025",
    "collateralAsset": "CIRBTC",
    "loanId": "fc988ed5-c129-4f70-a064-e5beb7eb8e32",
    "txHash": "0x3c4d5e6f70819293a4b5c6d7e8f90a1b2c3d4e5f60718293a4b5c6d7e8f9aabb",
    "createDate": "2026-06-25T10:15:00.000Z",
    "updateDate": "2026-06-25T10:17:00.000Z"
  }
}

Confirm the updated position

Fetch the loan to confirm the added collateral is reflected and the health factor has improved:

curl https://api-sandbox.circle.com/v1/borrow/loans/fc988ed5-c129-4f70-a064-e5beb7eb8e32 \
  -H "Authorization: Bearer $API_KEY"

collateralAmount on the loan should now include the added amount, and healthFactor should be higher than it was before.

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How-to: Add collateral to a loan

Prerequisites

Steps

​Prerequisites

​Steps

Prerequisites

Steps