diff --git a/xdrip/Constants/ConstantsNightScout.swift b/xdrip/Constants/ConstantsNightScout.swift
index 356ca3f5..06c793f0 100644
--- a/xdrip/Constants/ConstantsNightScout.swift
+++ b/xdrip/Constants/ConstantsNightScout.swift
@@ -11,4 +11,7 @@ enum ConstantsNightScout {
     /// if the time between the last and last but one reading is less than minimiumTimeBetweenTwoReadingsInMinutes, then the last reading will not be uploaded - except if there's been a disconnect in between these two readings
     static let minimiumTimeBetweenTwoReadingsInMinutes = 4.75
     
+    /// there's al imit of 102400 bytes to upload to NightScout, this corresponds on average to 400 readings. Setting a lower maximum value to avoid to bypass this limit.
+    static let maxReadingsToUpload = 300
+    
 }
diff --git a/xdrip/Managers/NightScout/NightScoutUploadManager.swift b/xdrip/Managers/NightScout/NightScoutUploadManager.swift
index 91004886..6d4541fd 100644
--- a/xdrip/Managers/NightScout/NightScoutUploadManager.swift
+++ b/xdrip/Managers/NightScout/NightScoutUploadManager.swift
@@ -291,11 +291,23 @@ public class NightScoutUploadManager:NSObject {
         }
         
         // get latest readings, filter : minimiumTimeBetweenTwoReadingsInMinutes beteen two readings, except for the first if a dis/reconnect occured since the latest reading
-        let bgReadingsToUpload = bgReadingsAccessor.getLatestBgReadings(limit: nil, fromDate: timeStamp, forSensor: nil, ignoreRawData: true, ignoreCalculatedValue: false).filter(minimumTimeBetweenTwoReadingsInMinutes: ConstantsNightScout.minimiumTimeBetweenTwoReadingsInMinutes, lastConnectionStatusChangeTimeStamp: lastConnectionStatusChangeTimeStamp, timeStampLastProcessedBgReading: timeStamp)
+        var bgReadingsToUpload = bgReadingsAccessor.getLatestBgReadings(limit: nil, fromDate: timeStamp, forSensor: nil, ignoreRawData: true, ignoreCalculatedValue: false).filter(minimumTimeBetweenTwoReadingsInMinutes: ConstantsNightScout.minimiumTimeBetweenTwoReadingsInMinutes, lastConnectionStatusChangeTimeStamp: lastConnectionStatusChangeTimeStamp, timeStampLastProcessedBgReading: timeStamp)
         
         if bgReadingsToUpload.count > 0 {
             trace("    number of readings to upload : %{public}@", log: self.oslog, category: ConstantsLog.categoryNightScoutUploadManager, type: .info, bgReadingsToUpload.count.description)
             
+            // there's a limit of payload size to upload to NightScout
+            // if size is > maximum, then we'll have to call the upload function again, this variable will be used in completionHandler
+            let callAgainNeeded = bgReadingsToUpload.count > ConstantsNightScout.maxReadingsToUpload
+            
+            if callAgainNeeded {
+                trace("    restricting readings to upload to %{public}@", log: self.oslog, category: ConstantsLog.categoryNightScoutUploadManager, type: .info, ConstantsNightScout.maxReadingsToUpload.description)
+            }
+
+            // limit the amount of readings to upload to avoid passing this limit
+            // we start with the oldest readings
+            bgReadingsToUpload = bgReadingsToUpload.suffix(ConstantsNightScout.maxReadingsToUpload)
+            
             // map readings to dictionaryRepresentation
             let bgReadingsDictionaryRepresentation = bgReadingsToUpload.map({$0.dictionaryRepresentationForNightScoutUpload})
             
@@ -311,6 +323,19 @@ public class NightScoutUploadManager:NSObject {
                     
                     UserDefaults.standard.timeStampLatestNightScoutUploadedBgReading = timeStampLastReadingToUpload
                     
+                    // callAgainNeeded means we've limit the amount of readings because size was too big
+                    // if so a new upload is needed
+                    if callAgainNeeded {
+                        
+                        // do this in the main thread because the readings are fetched with the main mainManagedObjectContext
+                        DispatchQueue.main.async {
+                        
+                            self.uploadBgReadingsToNightScout(siteURL: siteURL, apiKey: apiKey, lastConnectionStatusChangeTimeStamp: lastConnectionStatusChangeTimeStamp)
+                            
+                        }
+                        
+                    }
+                    
                 }
                 
             })
@@ -387,6 +412,8 @@ public class NightScoutUploadManager:NSObject {
             // transform dataToUpload to json
             let dateToUploadAsJSON = try JSONSerialization.data(withJSONObject: dataToUpload, options: [])
 
+            trace("    size of data to upload : %{public}@", log: self.oslog, category: ConstantsLog.categoryNightScoutUploadManager, type: .info, dateToUploadAsJSON.count.description)
+
             if let url = URL(string: siteURL), var uRLComponents = URLComponents(url: url.appendingPathComponent(path), resolvingAgainstBaseURL: false) {
 
                 if UserDefaults.standard.nightScoutPort != 0 {