> ## Documentation Index
> Fetch the complete documentation index at: https://developers.circle.com/llms.txt
> Use this file to discover all available pages before exploring further.

# How-to: Add collateral to a loan

> Post additional cirBTC as collateral to an open loan to lower its LTV and restore its health factor after a margin call.

Post additional cirBTC as collateral against an open loan. Adding collateral
lowers the loan's
[LTV](/circle-mint/concepts/digital-asset-backed-borrowing#ltv-health-factor-and-liquidation)
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](/circle-mint/quickstarts/borrow-with-cirbtc)
  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

<Steps>
  <Step title="Submit the collateral request">
    Call
    [`POST /v1/borrow/loans/{id}/collateral`](/api-reference/circle-mint/digital-asset-backed-borrowing/add-borrow-loan-collateral)
    with the amount of cirBTC you want to add in raw `uint256` base units.

    ```bash theme={null}
    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`:

    ```json theme={null}
    {
      "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.
  </Step>

  <Step title="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}`](/api-reference/circle-mint/digital-asset-backed-borrowing/get-borrow-job)
    until you see the terminal state.

    ```json theme={null}
    {
      "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"
      }
    }
    ```
  </Step>

  <Step title="Confirm the updated position">
    Fetch the loan to confirm the added collateral is reflected and the health
    factor has improved:

    ```bash theme={null}
    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.
  </Step>
</Steps>