Medical Syringes and Needles: A Complete Guide to Use, Selection, and Recommendations

A syringe and a needle seem like the simplest supplies in any practice. Yet the choice decides how precisely you deliver a dose, how much the injection hurts, how fast a blood draw flows and, above all, whether someone on the team gets stuck at the end.

This guide brings together everything you need to know: how a syringe is built, the difference between Luer Slip and Luer Lock, how to read a needle's gauge and color, which needle to choose for each route of administration, how to work with insulin syringes, how to draw blood with a vacutainer, and what to do with used needles. At every step you'll find the right products from the Prima Shop catalog.

How a syringe with needle is built

Before types and sizes, it's worth knowing what each part is called. That way you read a product sheet correctly and know exactly what you're ordering.

Disposable syringes differ in three ways: volume, how the needle attaches, and intended use. The table below helps you tell them apart quickly.

Luer Slip or Luer Lock?

Both follow the same tip geometry, so a standard needle fits either one. The difference is how it stays attached.

2-part or 3-part?

3-part syringes have a rubber stopper on the plunger: they glide evenly, without jerking, and you dose more precisely. 2-part syringes have no stopper, are cheaper, and are suitable for drawing up and transferring liquids or for non-medical use. For injections, generally choose 3-part syringes.

Which volume to choose

The simple rule: the smallest syringe that holds the dose. A 0.4 ml dose measured in a 10 ml syringe is read almost at random; in a 1 ml syringe, precisely. Still, leave a little room for expelling air.

• PRIMA 3-part Luer Lock syringes have a transparent barrel, clear graduations, a plunger with rubber stopper, and are individually packaged with the needle included: 2/2.5 ml with 23G needle, 5 ml with 22G needle, 10 ml with 21G needle, 20 ml and 60 ml with 18G needle.
• 3-component Luer Slip syringes, with detachable needle: the plunger can be broken after injection so the syringe cannot be reused.
• Without needle, for when you choose the right needle separately: 2/2.5 ml, 5 ml and 10 ml, 2-part Luer Slip.
• For tube feeding and irrigation: PRIMA 100 ml Guyon syringes, sterile, 3-part. To temporarily close a Luer Slip syringe: rubber caps.

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36²⁹Lei

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PRIMA 5ml Luer Lock Syringes with 22G Needle, 100 pcs

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35⁷⁰Lei

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PRIMA Luer Lock Syringes 10 ml with 21G Needle, 100 pcs

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49²⁵Lei

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PRIMA Luer Slip Syringes 2 ml with 23G Blue Needle, 100 pcs

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33⁸⁸Lei

excl. VAT: 28,00 Lei

PRIMA Luer Slip Syringes 5 ml with 21G Green Needle, 100 pcs

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34⁴⁹Lei

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PRIMA 10ml Luer Slip Syringes, Without Needle, Disposable, 100 pcs

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47¹⁹Lei

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A needle box reads, for example, 21G × 1½″ (0.8 × 38 mm). The first number is the gauge, i.e. the outer diameter: the higher the number, the thinner the needle. Next comes the length in inches and, in parentheses, the diameter and length in millimeters.

So you don't have to read the label on every needle, the hub has a color standardized by ISO 6009: a green needle is 21G from any manufacturer that follows the standard.

Length: inches and millimeters

Length is chosen according to how deep the substance needs to go. The conversions you'll see most often: ½″ = 13 mm, ⅝″ = 16 mm, 1″ = 25 mm, 1¼″ = 32 mm, 1½″ = 38 mm. A needle too short for an intramuscular injection leaves the drug in fatty tissue; one too long for a subcutaneous injection delivers it into muscle.

Which needle for each route of administration

Values are approximate. The final choice depends on the facility's protocol, the drug's package insert, and the patient's age and build.

• PRIMA sterile disposable needles, stainless steel, with colored hub and protective sheath, 100 per box: 18G pink, 19G, 20G yellow, 21G green, 22G black, 23G blue, 27G and 30G, 0.30 × 13 mm.
• For deep injections or patients with a thick fat layer: STERICAN 20G needles, 0.9 × 70 mm.

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PRIMA Sterile Medical Syringe Needles, Thick, Large, 18G, for Intravenous, Hypodermic Injections and Infusions, Pink, 1.20x38mm, 100 pcs

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16⁹³Lei

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PRIMA Syringe Needles, 21G, Long, Sterile, for Intravenous and Hypodermic Injections and Infusions, Green, 0.80x38mm, 100 pcs

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12⁹⁵Lei

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PRIMA Sterile Medical Syringe Needle, Thin, 27G, for Intravenous, Hypodermic Injection and Infusion, Gray, 0.4x13 mm, 100 pcs

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13⁹²Lei

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Insulin syringes are graduated in international units (IU), not milliliters, and are calibrated for a specific concentration. Vial insulin, the kind drawn up with a syringe, usually has a concentration of U-100: 100 units per milliliter. Higher concentrations, U-200 or U-300, exist only in pens and are not drawn up with a syringe. For U-100:

• Insulin syringes 0.5 ml, fixed 30G needle: 50 IU, 0.31 × 8 mm needle, plunger with stopper, ethylene oxide sterilized.
• PRIMA insulin syringes 1 ml, attached 29G needle: 0.33 × 13 mm, rubber plunger.
• PRIMA insulin syringes 1 ml, attached 27G needle: 0.4 × 13 mm, leak-tight, ethylene oxide sterilized.
• For small doses expressed in milliliters, not units: 1 ml tuberculin syringes with 25G needle. For insulin pens: PEN needles 29G × 12 mm, compatible with universal pens; since they are long, they are used with a skin fold, as directed by the physician.

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PRIMA Insulin Syringes 0.5 ml with Fixed Needle 30G 1/2" (0.30 x 13 mm), 100 pcs

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47¹⁹Lei

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PRIMA Insulin Syringes 1 ml with Fixed Needle 29G 1/2" (0.33 x 13 mm), 100 pcs

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48³⁹Lei

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PRIMA 1 ml Insulin Syringes with Fixed Needle 27G 1/2" (0.4 x 13 mm), 100 pcs

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40⁷⁸Lei

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Drawing blood with a syringe works, but the closed vacuum system is safer and faster: blood flows directly into the tube, in the correct amount for the additive it contains, without transfer from one container to another. You need three pieces:

1. The vacutainer needleIt has two points: one goes into the vein, the other, covered by a rubber sleeve, pierces the tube stopper. The sleeve closes again when you remove the tube, so no blood leaks. The standard for adults is 21G green.
2. The holderThe transparent holder into which the needle screws and into which you push the tubes one by one. It is single-use and is discarded together with the needle, without separating them.
3. The butterflyA short needle with wings and flexible tubing, for small or fragile veins, children, the elderly and hand draws. The wings give you fine control during venipuncture.

Order of draw

Additives in one tube can contaminate the next tube and alter results; for example, EDTA falsely raises potassium. That's why tubes are filled in a recommended order (CLSI GP41):

Cap colors may vary between manufacturers, and special tubes, such as those for ESR, are drawn according to the laboratory's procedure. Always follow the tube label.

• PRIMA 21G vacutainer needles, with rubber sleeve and protective cap, sterile. For smaller veins: 22G black; for high flow: 18G pink.
• PRIMA vacutainer holder, transparent, single-use, and butterfly blood collection needles with Luer Lock adapter, 21G, 0.8 × 19 mm.
• Sterile butterflies (scalp vein sets), with siliconized needle and 315 mm tubing, from 19G to 25G, including 23G blue for fragile veins.
• Tubes: coagulation, chemistry with activator, red cap, hematology K3 EDTA and ESR with citrate. For blood gas analysis: 2 ml heparinized syringes.

Pentru recoltarea de sânge

PRIMA Sterile Vacutainer Needles, 21Gx1 1/2, Green, 100 pcs

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35⁰⁹Lei

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Blood Collection Holder for Vacutainer, PRIMA, Luer Lock, 100 pcs

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25⁴¹Lei

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Sterile Butterfly Infusion Sets with 21G Needle - Green - 100 pcs

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35⁰⁹Lei

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Beyond the syringe: IV cannulas

When a patient needs multiple intravenous administrations or an infusion, instead of repeated sticks an IV cannula (peripheral venous catheter) is placed. Choose the smallest gauge that allows the treatment: 20–22G for most adult infusions, 18G and larger for high flow, 24–26G for children and very fragile veins. Secure the cannula with a dedicated sterile dressing and note the insertion date.

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PRIMA Color-Coded IV Cannulas, 14G - 26G, with Wings and Catheter, 100 pcs

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95⁵⁹Lei

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Color-Coded IV Cannulas, 14G - 26G, with Wings and Catheter, PRIMA, 100 pcs

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95⁵⁹Lei

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PRIMA Sterile IV Cannula Fixation Dressings, PPSB, 8x6 cm, 50 pcs

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17⁵⁵Lei

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Safe injection, step by step

Most injection-related incidents come not from technique but from preparation and what happens afterward. The steps below follow the World Health Organization's best practice principles for injections.

1. Hand hygiene and a clean work areaPrepare the medication on a clean surface, separate from the area where blood samples and waste are kept.
2. Check the packaging and expiration dateSterility is guaranteed only as long as the blister pack is intact. Wet, torn or open packaging means the syringe gets thrown away.
3. Disinfect the vial stopper and let the alcohol dryUse a 70% alcohol pad on the rubber stopper and wait until it is completely dry: that way it works and doesn't get into the medication.
4. A new syringe and a new needle for every injectionNever reinsert a used syringe or needle into a multi-dose vial, not even for the same patient, and don't leave a needle stuck in the stopper.
5. Expel the air and check the dose at eye levelHold the syringe upright, needle up, tap the barrel gently and push the bubbles out. Read the dose at the edge of the stopper.
6. Disinfect the skin and wait for it to dryOn skin that is still wet, alcohol stings and disinfects less effectively.
7. Inject at the angle and depth appropriate to the routeWithdraw the needle along the same path and apply a sterile gauze swab, without massaging the site for subcutaneous injections.
8. Immediately discard the syringe with needle in the sharps containerWithout recapping, without detaching the needle, and without leaving the syringe on the tray "for later".

Pentru pregătire: tampoane cu alcool, comprese, garou

PRIMA Sterile Alcohol Prep Pads, 6.5 x 3 cm, 100 pcs

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Sterile Gauze Swabs, PRIMA, 10x10cm, 25 pcs

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1²⁰Lei

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PRIMA Elastic Textile Medical Tourniquet with Quick Release, Blue, 2.5cm x 40cm

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7²⁵Lei

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Needlestick injuries almost always happen after the injection: when recapping, detaching the needle, clearing the tray, or with an overfilled container. Directive 2010/32/EU on the prevention of sharp injuries in the hospital and healthcare sector calls for eliminating exactly these actions. In Romania, medical waste collection follows Ministry of Health Order no. 1226/2012.

• ADR-certified plastic sharps containers: 1 liter for the treatment tray, 3 liters, 5 liters, 7 liters and 12 liters for the blood collection room.
• Biosafe Line containers, rigid polypropylene, in several volumes, for needles, blades and scalpels. For travel or home treatments: the yellow 0.75 liter container.
• For other infectious waste: boxes with Biohazard bag of 10, 20 and 40 liters.

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19³⁵Lei

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from 4,53 lei

Sharps Containers – Biosafe Line

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4⁸⁶Lei

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What to check on the packaging

Common mistakes

• Recapping the needleTwo-handed recapping is the most common cause of needlesticks. The syringe with needle goes straight into the container.
• Changing only the needle and reusing the syringeThe syringe becomes contaminated through backflow, even if you can't see it. The syringe and needle are both single-use.
• Going by color alonePink means 18G for hypodermic needles but 20G for IV cannulas. Read the number on the hub or packaging.
• Using a U-100 syringe for another insulin concentrationThe dose ends up 2.5 times off. The syringe must have the same concentration as the insulin.
• Measuring a small dose in a large syringeHalf a milliliter in a 20 ml syringe can't be read precisely. Choose the smallest syringe that holds the dose.
• Leaving a needle stuck in a multi-dose vialThe needle becomes an entry point for microorganisms into the whole vial.
• Using a Guyon syringe for injectionsIts tip is made for feeding tubes and irrigation, not for needles or intravenous lines.
• Filling the sharps container up to the lidNeedles poke out through the opening when you add another. Close it permanently at the marked line.

What to choose, in short, for each situation

Frequently asked questions