Water and weight logs

Use client.waterLogs and client.weightLogs to record water intake and body weight and read them back as one value per day. These examples use the client from Authentication. Its token needs the water_logs:read, water_logs:write, weight_logs:read, and weight_logs:write scopes; without them, calls fail with an .authorization error whose code is scope_insufficient.

Lists take inclusive yyyy-MM-dd dates in the client's timezone (days and dates). A list returns at most 100 days, the most recent ones when more match, and start can be at most five years before today; an earlier start fails with the code date_range_too_large. To chart a longer range, such as a year, request windows of 100 days or fewer and merge them.

Creates aren't idempotent: after a timed-out create, list the day before you retry, or the entry may be recorded twice (retries).

Log water

do {
    let log = try await client.waterLogs.create(
        amount: WaterAmount(value: 8, unit: .fluidOunces),
        consumedAtUTC: ISO8601DateFormatter().string(from: drankAt)
    )
    savedWaterLogIDs.append(log.id) // You need the ID to delete the entry.
} catch let error as JanuaryError where error.code == "daily_water_limit_exceeded" {
    showInputError("That would take today's water past 24 L.")
}

An amount is 1–811.5 fluid ounces (.fluidOunces), 0.1–101.4 US cups (.cups, 8 fluid ounces each), or 30–24,000 milliliters (.milliliters). Send the unit the user entered: the minimums don't convert evenly (1 fl oz ≈ 29.6 ml, below the 30 ml minimum). consumedAtUTC takes ISO 8601 with any offset and defaults to now.

Each user can log up to 24 L a day. The cap counts the UTC calendar day of consumedAtUTC, whatever offset you send, while lists group days in the client's timezone, so near midnight a listed day's total can differ from what the cap counted. A create over the cap fails with the code daily_water_limit_exceeded (a .validation error).

Daily water totals

let totals = try await client.waterLogs.list(start: "2026-09-01", end: "2026-09-30", unit: .milliliters)
for day in totals.items {
    print(day.date, day.total.value, day.total.unit)
}

Totals are in the unit you ask for (fluid ounces by default), oldest day first. Days with no water are left out, so items can be empty.

Delete a water log

try await client.waterLogs.delete(id: log.id)

Deleting an unknown or already deleted log also succeeds, so retrying a delete is safe.

Log a weight

let weightLog = try await client.weightLogs.create(
    weight: Weight(value: 68.5, unit: .kilograms),
    measuredAtUTC: ISO8601DateFormatter().string(from: measuredAt)
)

A weight is 10–1,000 pounds or 4.5–453.6 kilograms. Weight logs have no ID and can't be updated or deleted. Every measurement is kept, and a day shows the one with the latest measuredAtUTC, so to change what a day shows, log a newer measurement for that day.

Daily weights

let weights = try await client.weightLogs.list(start: "2026-09-01", end: "2026-09-30")
for day in weights.items {
    print(day.date, day.weight.value, day.weight.unit)
}

Each weight is in the unit it was logged in, oldest day first. Only days with a weight appear.

Next: Glucose prediction.