diff --git a/ClickHouse.Client.Tests/TestUtilities.cs b/ClickHouse.Client.Tests/TestUtilities.cs
index 59b5e941..93974493 100644
--- a/ClickHouse.Client.Tests/TestUtilities.cs
+++ b/ClickHouse.Client.Tests/TestUtilities.cs
@@ -164,7 +164,11 @@ public static IEnumerable<DataTypeSample> GetDataTypeSamples()
             if (SupportedFeatures.HasFlag(Feature.WideTypes))
             {
                 yield return new DataTypeSample("Int128", typeof(BigInteger), "toInt128(concat('-1', repeat('0', 30)))", -BigInteger.Pow(new BigInteger(10), 30));
-                yield return new DataTypeSample("UInt128", typeof(BigInteger), "toInt128(concat('1', repeat('0', 30)))", BigInteger.Pow(new BigInteger(10), 30));
+                yield return new DataTypeSample("Int128", typeof(BigInteger), "toInt128('170141183460469231731687303715884105727')", BigInteger.Parse("170141183460469231731687303715884105727"));
+                yield return new DataTypeSample("Int128", typeof(BigInteger), "toInt128('-170141183460469231731687303715884105728')", BigInteger.Parse("-170141183460469231731687303715884105728"));
+
+                yield return new DataTypeSample("UInt128", typeof(BigInteger), "toInt128(concat('1', repeat('0', 30)))", BigInteger.Pow(new BigInteger(10), 30));                
+                yield return new DataTypeSample("UInt128", typeof(BigInteger), "toUInt128('340282366920938463463374607431768211455')", BigInteger.Parse("340282366920938463463374607431768211455"));
 
                 yield return new DataTypeSample("Int256", typeof(BigInteger), "toInt256(concat('-1', repeat('0', 50)))", -BigInteger.Pow(new BigInteger(10), 50));
                 yield return new DataTypeSample("UInt256", typeof(BigInteger), "toInt256(concat('1', repeat('0', 50)))", BigInteger.Pow(new BigInteger(10), 50));
diff --git a/ClickHouse.Client/Types/AbstractBigIntegerType.cs b/ClickHouse.Client/Types/AbstractBigIntegerType.cs
index e20457da..4b566f36 100644
--- a/ClickHouse.Client/Types/AbstractBigIntegerType.cs
+++ b/ClickHouse.Client/Types/AbstractBigIntegerType.cs
@@ -11,7 +11,17 @@ internal abstract class AbstractBigIntegerType : IntegerType
 
         public override Type FrameworkType => typeof(BigInteger);
 
-        public override object Read(ExtendedBinaryReader reader) => new BigInteger(reader.ReadBytes(Size));
+        public override object Read(ExtendedBinaryReader reader)
+        {
+            if (Signed)
+                return new BigInteger(reader.ReadBytes(Size));
+
+            var data = new byte[Size + 1];
+            for (int i = 0; i < Size; i++)
+                data[i] = reader.ReadByte();
+            data[Size] = 0;
+            return new BigInteger(data);
+        }
 
         public abstract override string ToString();
 
@@ -30,13 +40,20 @@ public override void Write(ExtendedBinaryWriter writer, object value)
                 _ => new BigInteger(Convert.ToInt64(value, CultureInfo.InvariantCulture))
             };
 
+            if (bigInt < 0 && !Signed)
+                throw new ArgumentException("Cannot convert negative BigInteger to UInt");
+
             byte[] bigIntBytes = bigInt.ToByteArray();
             byte[] decimalBytes = new byte[Size];
 
-            if (bigIntBytes.Length > Size)
-                throw new OverflowException();
+            var lengthToCopy = bigIntBytes.Length;
+            if (!Signed && bigIntBytes[bigIntBytes.Length - 1] == 0)
+                lengthToCopy = bigIntBytes.Length - 1;
+
+            if (lengthToCopy > Size)
+                throw new OverflowException($"Got {lengthToCopy} bytes, {Size} expected");
 
-            bigIntBytes.CopyTo(decimalBytes, 0);
+            Array.Copy(bigIntBytes, decimalBytes, lengthToCopy);
 
             // If a negative BigInteger is not long enough to fill the whole buffer,
             // the remainder needs to be filled with 0xFF
diff --git a/ClickHouse.Client/Types/IntegerType.cs b/ClickHouse.Client/Types/IntegerType.cs
index fff054e8..419f3305 100644
--- a/ClickHouse.Client/Types/IntegerType.cs
+++ b/ClickHouse.Client/Types/IntegerType.cs
@@ -2,5 +2,6 @@
 {
     internal abstract class IntegerType : ClickHouseType
     {
+        public virtual bool Signed => true;
     }
 }
diff --git a/ClickHouse.Client/Types/UInt128Type.cs b/ClickHouse.Client/Types/UInt128Type.cs
index 43c45dea..3da46013 100644
--- a/ClickHouse.Client/Types/UInt128Type.cs
+++ b/ClickHouse.Client/Types/UInt128Type.cs
@@ -1,9 +1,14 @@
-namespace ClickHouse.Client.Types
+using System.Numerics;
+using ClickHouse.Client.Formats;
+
+namespace ClickHouse.Client.Types
 {
     internal class UInt128Type : AbstractBigIntegerType
     {
         public override int Size => 16;
 
         public override string ToString() => "UInt128";
+
+        public override bool Signed => false;
     }
 }
diff --git a/ClickHouse.Client/Types/UInt256Type.cs b/ClickHouse.Client/Types/UInt256Type.cs
index 54609d9e..e2d7039a 100644
--- a/ClickHouse.Client/Types/UInt256Type.cs
+++ b/ClickHouse.Client/Types/UInt256Type.cs
@@ -1,9 +1,14 @@
-namespace ClickHouse.Client.Types
+using System.Numerics;
+using ClickHouse.Client.Formats;
+
+namespace ClickHouse.Client.Types
 {
     internal class UInt256Type : AbstractBigIntegerType
     {
         public override int Size => 32;
 
         public override string ToString() => "UInt256";
+
+        public override bool Signed => false;
     }
 }