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Which Knot: Blood Knot or Surgeon’s?

by Philip Monahan

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Question: Blood knot or surgeon’s knot, and why?

Evan P., Berkeley, CA

Answer: I am a blood-knot guy. It’s the one I learned first, and I’ve tied it enough that I can tie a blood knot well every time (pretty quickly, I might add). Plus, it’s a beautiful knot—elegant and symmetrical.

But why take my word for it? I threw the question out to the usual suspects, and here’s what they had to say:

Blood KnotThe Blood Knot is one of the first “complicated” connections that most fly fishers learn, but it becomes easy to tie with practice and makes a slimmer connection.
Illustration by Jonathan Milo.

Brant Oswald, guide and fly-fishing instructor: I am a blood knot guy, too, for similar reasons.

My issue with a double surgeon’s is that—even when formed correctly—the knot does not always draw up correctly for maximum strength.  If one strand cuts across the other as the knot rolls over into the figure 8 as it is tightened, the knot will be quite weak, and it is not due to any error on the part of the angler tying the knot.  My mantra when I teach a surgeon’s knot to beginners is to test, test, test the knot before it is fished.  This is true for any knot, but absolutely critical with a surgeon’s.

I hardly ever use a surgeon’s knot in my own fishing.  It does have advantage of allowing two sections of material of relatively dissimilar diameters to be joined together, but this is usually only important in an emergency situation, say to cobble together a usable leader in the last couple of minutes of light.

The surgeon’s knot is much bulkier, which is usually not an issue if it is only used only with smaller sizes of tippet material.  However, if an angler is building hand-tied leaders or making connections in the heavier part of the leader (e.g., butt section to the butt of a new leader), then the blood knot’s slimmer profile is a distinct advantage.  And the right angle tag ends of a blood knot offer opportunities in rigging: tandem flies with one on the point and one on the blood knot dropper, a nymph on the point with extra weight attached to the dropper, etc.

And, like Phil, I admit that a big part of my attachment to the blood knot is aesthetic. I watch thousands of them come together in my hands every season, and there is still something very satisfying about drawing up a well-tied blood knot.

Tom Rosenbauer, author of the Orvis Fly-Fishing Guide: I use a blood knot if the diameters are within .001 inches.  I tie a triple surgeon’s if they are not, or if I’m going from Fluoro to mono. Why? Because I trust the triple surgeon’s more when materials differ.

Lori-Ann Murphy, co-founder of Reel Women, and fishing and guest relations host of El Pescador Lodge: I recognize that the surgeon’s knot is stronger—especially when it involves attaching materials that differ more than the 2-size grace rule we use with blood knots—but I’m a blood-knot gal ‘cuz it is so beautiful and streamlined.

Surgeons KnotThe Double Surgeon’s Knot is easier for many anglers to tie — especially in low light or adverse conditions.
Illustration by Jonathan Milo.

Ted Leeson, author: Blood knot for me, partly because I tie my own leaders, and surgeon’s knots are unsuitable for the purpose, and partly I like its symmetry.  I think blood knots get a bad rap for two reasons: first, people think they are hard to tie, but that’s just a matter of practice.  And secondly, they think blood knots are weaker.  I’ve actually talked to a number of line manufacturers and independent testers about the relative strength of the two knots.  Many people insist that the surgeon’s knot is stronger, which may be the case.  But I spoke with a person at DuPont (which makes various brands of monofilament) who told me that, in tests, the relative strength of the two knots varies a good bit with the person tying them.  Under “ideal” circumstances, if such things exist, a surgeon’s knot may be intrinsically stronger, but for any given angler, it might not be.  In the end, go with what you tie best, unless you’re building leaders, in which case there’s no substitute for a blood knot, at least in the butt and midsections.

Dave Kumlien, guide and executive director of the Whirling Disease Foundation: I used to tie the blood knot but switched to the surgeon’s about 30 years ago.  The surgeon’s is easier to tie, a bit stronger, and can be tied large under poor light with cold hands and pulled “small.” The blood knot doesn’t offer this option.  Plus, I’ve taught fly fishing and fly casting for over 35 years, and I teach the surgeon’s both as a tippet knot and a tie-on-the-fly knot to beginning fly fishers.

I was shown the surgeon’s loop as a tie-on-the-fly knot many years ago by Al Troth, and it works great.  I use it myself, all the time.  By using the surgeon’s for a tippet and a fly knot, I am able to teach the beginning fly fisher one knot, the surgeon’s, which covers all their on-the-water-knot needs.  The drawback to the surgeon’s is that it uses up more tippet material, and it clearly is not as elegant as the blood knot.

Ben Romans, angling writer: Well, I have a confession to make: I use an improved clinch knot to splice tippet. I know, I know, that probably goes against fly-fishing 101 protocol, but I’ve gotten so good at tying that knot over the years that I use it whenever I’m in a rush. Don’t ask me how I do it because I’ve showed dozens of people and most don’t have the finger dexterity to do it.

That said, my opinion is probably moot—but I’ll give it to you anyway. When I don’t tie the clinch, I tie the blood. It’s very similar to the clinch, so I can form the needed wraps in a jiffy, and in my little world, I remain convinced it’s stronger than a surgeon’s knot. I also feel like I waste less material (long tag ends) tying a clinch or blood versus a surgeon’s.

Joe Healy, editor of Fly Rod & Reel: Surgeon’s because it’s never failed me and is a bit easier to tie than the blood, particularly with cold hands.

Matt Supinski, Great Lakes guide: The blood knot is good, pretty, and goes through the guides of the rod smoother than a surgeon’s. BUT, only if similar diameters of leader are used. If you’re attaching two quite different diameters, the blood knot may fail.

The surgeon’s is very strong on all differing sizes of leader—a triple surgeon’s is better than a double—but you MUST lubricate the knot with saliva and slowly draw the loops together for a smoother, more blood-knot-looking surgeon’s knot.

Steve Hemkens, head of fly-fishing product development for Orvis: I like the blood knot for its symmetry and for tying materials of dissimilar diameters. I also like it for building out a leader that gets too short where I need to add a few sections because it’s straight, whereas a surgeon’s has a bit of a kink. I like the improved blood a lot for tying together two dissimilar materials together, even though it’s not a 100% knot like the slim beauty.

I find that a blood is easier for a beginner to tie, provided they use their thumbnail, if they have one, to help isolate both tags and pull them through. I have heard through the grapevine that a triple surgeon’s is a stronger knot, so I usually use that when I’m being lazy, but I am a blood knot man.

MidCurrent Fly Fishing
Phil Monahan is a former Alaskan guide and was the long-time editor of American Angler magazine. He's now a columnist for MidCurrent and writes and edits the fly-fishing blog at You can email your fly fishing questions to us at
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  • Larry clark

    I’ve tested the surgeon’s knot against the blood knot by tying three sections of leader material together with each and then stretching the length of leader until it breaks. Almost every time it’s the surgeon knot that fails.

  • Julia Horncastle

    Can anyone trace the origins of the naming of the blood knot? 

  • adam apple

    Dude, if you’re gonna spend all that money to buy a leader – especially if you’re gonna buy flourocarbon – why the hell would you make a knot that leaves an angle on your tippet? A beautiful, elegant leader and tippet with a kink in it? No thanks, dudes. I decided I wanted a perfect, straight connection when I tied on new tippet. I wanted something perfect. Not a bulky knot with a freaking angle on my line. So, I just took the time to practice the blood knot. I practiced it on my breaks at my desk at work. I practiced it for a few minutes every day at home. And then something wonderful happened. I began making perfect blood knots over and over again, quickly and efficiently. Thanks God for the blood knot!

  • David Hutton

    I prefer the blood knot. It is a PITA to tie, but it cant be beat,

  • John Davenport

    Only Steve uses the blood knot for dissimilar diameters. Did he misspeak? To add some more tippet in the middle of a multi-fly rig you pretty much have to use a blood knot. The international competitors in the America Cup Fly Fishing Tournament in Vail all seemed to use the blood knot tag to drop off intermediate flies.

  • Roger Hickson

    I use the surgeon even though I find it harder to tie than the blood knot. I used to find when I tied both it was always the blood that broke first no matter where it was in the leader but agree if you are replacing the middle of the leader the blood is the way to go if you don’t want to tie the whole leader.

  • seventyeighteen

    J knot, lays straighter than a surgon’s knot and is a lot easier to tie than a blood knot.

  • B

    I tie an over hand knot to start my blood knot…turns it into 2 abutting clinch knots. Was originally an error in tying, but I find it to be fast and strong.

  • rbob

    Double uni knot works for me!

    • genelarson

      I use it too, lot easier to control than the blood and I like the looks of it.

  • Fishnpond

    I actually tie two clinch knots that abut by making a loop of each end of the Tippett material then tying a clinch around that. I can tie them fast and in cold weather conditions. I haven’t had any problems with it and started tying it several years ago.

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  • Bob White

    Blood knot for me… for no other reason than it’s what I grew up with, I can tie one without thinking, and I like the trim symmetry of it.

    Old dogs, new tricks… meh.

  • Robert Moore

    Surgeon’s, blood knot to difficult to tie with usually cold hands…..never seems to break.

  • Bob LeMay

    In recent years I’ve switched to using a Slim Beauty for almost all of my splices with lines of dis-similar diameter (or completely different materials such as fluoro to mono). Once you’ve learned to tie it you can make the connection even when you can’t see in low light or at 2Am… The connection is very, very strong (pretty near 100% of line strength…).

    Although it was originally used as a big game knot for granders, etc down under (anytime I see “Beauty” I’m thinking of Oz…) it’s the best connection I know for single strength leader material of any size. It slides right through line guides even when under heavy pressure if trimmed properly (right up to the knot on each side.. Hope this helps

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  • Ken Morris

    I seem to fundamentally not understand the double surgeon’s knot. Every single picture confuses me. The blood knot instructions make more sense so…

  • NY Teacher

    Last season I discovered the Japanese Figure 8 for splicing tippet material. Very fast, very easy, strong, reliable, and, unlike the surgeon’s knot. it runs straight. I no longer dread splicing tippet during a good hatch with fading light. I have found no reason to use any other splice knot since. Try it, you’ll love it:! (See limp cobra)

  • Steve Tedesco

    Slim Beauty will win every time in a knot off with the blood and surgeons. Listen to Bob.

  • Paul

    No one has mentioned what i think is one of the best advantages of the blood knot. If you are on stream and fishing a two or three fly rig and have to reconnect the tippet to the leader it is a challenge to thread the tippet end through the loop to tie a surgeons knot. The blood not does not involve the both end of the tippet. One needs to manipulate only the end of the tippet that will meet the leader. My recommendation – Learn the blood not, it isn’t that difficult.

  • guido

    I like the blood knot for the same reason as Paul. Only my main thing is I can tie the one end of the tippet off a lanyard and not have to pre-cut the tippet or chase loose ends around.