Lantus SoloStar (Insulin Glargine) – A Complete Guide

Lantus Solostar is a long-acting basal insulin. It is used by people with type 1 diabetes and type 2 diabetes to keep blood glucose steady between meals and overnight. This article explains, in simple language, what Lantus is, how it works, who it may suit, and how to use it safely and confidently.

If you would like a broader overview of diabetes before you dive in, you may find it helpful to read How is diabetes treated? or Managing diabetes with insulin – is it necessary? and then come back to this page.

What is Lantus Solostar?

Lantus is the brand name for insulin glargine U100, a laboratory-made version of human insulin. It is designed to release slowly and evenly over about 24 hours, which is why we call it a “long-acting basal insulin”. The Solostar pen is a pre-filled device that lets you dial up your dose and inject it under the skin.

Unlike rapid-acting insulins such as Fiasp (fast-acting insulin aspart) , Lantus is not meant to cover the rise in glucose from a specific meal. Its job is to provide a steady background level of insulin all day and all night, similar to what a healthy pancreas would release in the background.

Many people using Lantus also take other medications such as metformin , GLP-1 medications like Ozempic or Trulicity, SGLT2 inhibitors, or rapid-acting insulin for meals. Lantus is often the “base” on which other treatments are added if needed.

How does Lantus work in the body?

Insulin acts like a key that opens tiny “locks” on the surface of muscle and fat cells, allowing glucose to move from the bloodstream into the cells where it can be used for energy. In insulin resistance , the locks do not respond properly, so more insulin is needed.

Lantus has been designed so that, once injected under the skin, it forms tiny crystals. These crystals slowly dissolve over many hours, releasing small, steady amounts of insulin into the bloodstream. This gives Lantus a relatively “flat” profile with no strong peak, which helps:

• Keep fasting and between-meal glucose levels more stable
• Reduce the risk of overnight lows compared with older intermediate insulins
• Provide a predictable background on which to build your overall treatment plan

In people with type 1 diabetes, Lantus replaces the background insulin that the pancreas can no longer produce. In people with type 2 diabetes, it supports the pancreas when it can still make some insulin but not enough to keep sugars in target.

How does Lantus differ from other insulins?

There are several groups of insulin with different speeds of action. You can see a full overview in Managing diabetes with insulin – is it necessary? but in brief:

• Rapid-acting insulins (for example Fiasp, Novorapid) start working within minutes and are used for meals and corrections.
• Long-acting basal insulins (for example Lantus, Levemir, Tresiba) have a slow, steady effect to cover background needs.
• Premixed insulins (for example Ryzodeg ) contain both basal and rapid insulin in one injection.

Lantus sits in the basal insulin group. It is usually taken once daily, although some people do better with two smaller doses (for example morning and evening). Your diabetes team will guide you on the best schedule for your situation.

Who is Lantus Solostar for?

Lantus can be used in adults and children with both type 1 and type 2 diabetes. How and why it is used is different in each condition.

Type 1 diabetes

In type 1 diabetes, the pancreas makes little or no insulin. People usually need:

• A basal insulin (for example Lantus) once or twice daily, and
• A rapid-acting insulin for meals and corrections.

Together, this is called a “basal–bolus” regimen. Lantus provides the background coverage, while meal-time insulin handles the food you eat.

Type 2 diabetes

In type 2 diabetes, insulin resistance and a gradual decline in insulin production mean that tablets alone are not always enough over time. Lantus is often added when:

• HbA1c remains above target despite tablets such as metformin and other agents
• Fasting or pre-breakfast glucose levels are high
• There are symptoms of high glucose, such as thirst, tiredness, or frequent urination

Many people feel anxious about “starting insulin”. If that is you, I would encourage you to read Managing diabetes with insulin – is it necessary? and Type 2 diabetes complications so you can see how good glucose control now can prevent problems later.

If you would like more structured support to get on top of your diabetes while using insulin, you may also be interested in the Type 2 Diabetes personalised online program or my free diabetes masterclass webinar .

How to use Lantus Solostar

Always follow the specific advice from your doctor or diabetes educator. The points below are a general guide to help you understand what you are doing and why.

When to take Lantus

Lantus is usually taken once a day at the same time each day. It does not have to be taken with food, but choosing a regular time (for example after your evening meal or at bedtime) makes it easier to remember.

Some people use Lantus twice daily (for example breakfast and bedtime) if a single dose does not last long enough. This is an individual decision, guided by your glucose patterns.

Where to inject

Lantus is injected into the fatty layer just under the skin (subcutaneous tissue). Common sites include the abdomen, thighs, or buttocks. Rotate sites within the same area to reduce the risk of lumps or lipohypertrophy.

Basic steps with the Solostar pen

1. Check the label to make sure you have Lantus Solostar, not another insulin.
2. Attach a new needle, remove the caps, and prime as instructed in your training.
3. Dial up the correct dose in units as agreed with your diabetes team.
4. Insert the needle into the chosen injection site.
5. Press the injection button all the way down and count slowly to 10.
6. Remove the needle and dispose of it safely in a sharps container.

For a refresher on storing and handling insulin safely, you can read Where do you store your insulin?

Typical starting doses and titration

Starting doses are individual. A common approach in adults with type 2 diabetes is to begin with a small once-daily dose (for example 10 units) and then adjust every few days based on fasting blood glucose readings. Your team may use a simple titration guide such as:

• Increase by 2 units if fasting glucose has been above target for several days
• Hold the dose if fasting glucose is in target
• Reduce the dose if you are having night-time or morning hypos

Target fasting levels are usually discussed with your doctor and may vary depending on your age, other medical conditions, and risk of hypoglycaemia. You can track your readings using the blood glucose (BSL) tool or the HbA1c tool on this website.

Storing Lantus

Unopened Lantus pens should be kept in the fridge (not in the freezer) between 2–8 °C. Once a pen is in use, it can usually be kept at room temperature for a limited period as stated in the product leaflet. Avoid leaving pens in very hot places, such as a parked car or on a sunny windowsill.

Side effects and safety

The most important possible side effect of Lantus, as with all insulin, is low blood glucose (hypoglycaemia). The risk is higher if:

• You take more insulin than your body needs
• You miss or delay meals
• You drink alcohol without eating
• Your kidney function changes

It is important that you know how to recognise and treat a hypo. I recommend reading How to treat a hypo without spinning your sugars into the twenties and discussing a personalised plan with your diabetes team.

Other side effects of Lantus may include:

• Mild weight gain when insulin is first started
• Redness, itching, or small lumps at injection sites
• Very rarely, allergic reactions

If you notice persistent lumps, swelling, or unpredictable glucose readings at a usual site, change area and let your clinician know. Regular rotation of injection sites is one of the simplest ways to keep insulin working predictably.

Getting the best results from Lantus

Lantus works best when it is part of a complete diabetes plan that also includes:

• A balanced eating pattern — see Type 2 diabetes friendly diet and How to reduce carbs in your diet .
• Regular movement and activity — even short walks or “exercise snacks” help improve insulin sensitivity. You might enjoy Exercise snacking – an easy way to lose weight .
• Weight management where appropriate — use the BMI tool and speak to your team about realistic goals.
• Attention to mental health and motivation — for example Type 2 diabetes and mental health or On the cycle of diabetes burnout .

If your HbA1c remains above target despite a well-titrated dose of Lantus, your team may discuss adding rapid-acting insulin for meals, switching to an insulin such as Ryzodeg , or using combinations with GLP-1 medications such as Xultophy, Ozempic, or Trulicity. These decisions are highly individual and should always be made with your clinician.

Remember that insulin is not a sign of failure. It is one of the most powerful tools we have to protect your eyes, kidneys, nerves, heart, and brain from the long-term effects of high glucose. Used well, Lantus can be a key part of getting your diabetes into the safest possible range.