If you've been switched to Merilog, you may be wondering which pen needles for Merilog SoloStar you should buy, since needles are not included with the pen. The good news: the SoloStar pen uses the same standard screw-on pen needles that many US patients already use. This guide covers fit, sizing, quantity, and a quick checklist before you order.
What Is Merilog SoloStar?
Merilog (insulin aspart-szjj) is a rapid-acting mealtime insulin made by Sanofi. In 2025 the FDA approved it as the first rapid-acting insulin biosimilar, referencing NovoLog. It comes in a vial and in a prefilled, disposable SoloStar pen, the same pen platform Sanofi uses for products like Lantus, Toujeo, and Admelog.
Because it is a disposable pen, you attach a new pen needle before each injection and remove it afterward. Your prescription or pharmacy may or may not include needles, so many people buy them separately.
Which Pen Needles Fit Merilog SoloStar?
SoloStar pens accept standard threaded pen needles. Widely used brands such as BD (Ultra-Fine and Nano) and NovoFine/NovoFine Plus are made to fit most major US insulin pens, including SoloStar. In practice, that means you can usually keep using the brand you already like.
- BD Ultra-Fine 31G 5mm Pen Needles (100 count): a common, comfortable everyday choice.
- NovoFine Plus 32G 4mm Pen Needles (100 count): one of the shortest and thinnest options available.
If a needle ever feels loose, cross-threaded, or won't seat fully, stop and attach a fresh one. Always check the pen's instructions for use and the needle box for compatibility information.
Best Pen Needle Size for Merilog SoloStar
Insulin is meant to go into the fat layer under the skin. Current injection guidance from diabetes organizations notes that short needles, like 4mm and 5mm, reach that layer for most adults regardless of body size, and are less likely to reach muscle.
- 4mm (32G): very short and thin; often recommended as a starting point for adults and children.
- 5mm (31G): slightly longer; a popular middle ground.
- 6mm and 8mm: still available, but many people use a skin lift with longer needles to avoid going too deep.
Higher gauge numbers mean thinner needles. Many people find 31G and 32G needles comfortable. Your healthcare provider can help you choose the right length and technique for you.
How Many Merilog SoloStar Pen Needles Do You Need?
Pen needles are designed for single use, so plan on one needle per injection. As a mealtime insulin, Merilog is often taken several times a day. The math is simple:
- 2 injections a day ≈ 60 needles a month
- 3 injections a day ≈ 90 needles a month
- 4 injections a day ≈ 120 needles a month
If you also use a long-acting insulin pen, add those injections to your total. A 100-count box covers about a month for many people, and value packs can lower the price per needle. For more detail, see our guide on how many pen needles you need per month.
Quick Checklist Before You Order
- Confirm the needle box lists compatibility with major insulin pens.
- Choose a length (4mm or 5mm is common) with your provider's input.
- Count your daily injections across all pens.
- Keep a small backup supply for travel or delayed refills.
- Have an FDA-cleared sharps container ready for disposal.
FAQ
Can I use the same needles I used with NovoLog FlexPen?
Usually yes. Standard brands such as BD and NovoFine are made to fit both FlexPen and SoloStar pens.
Can I reuse a pen needle?
No. Needles are single-use. Reuse can dull the tip, increase discomfort, and raise the risk of clogging or infection.
Should I leave the needle on between doses?
No. Remove it after each injection to help prevent leaks and air from entering the cartridge.
Ready to stock up? Browse all Zahrun pen needles. New customers can use code WELCOME10 for 10% off. As always, follow your healthcare provider's guidance for dosing and any medical decisions.
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