2026 update — How vaping (nicotine e‑cigarettes) affects insulin absorption and blood glucose control: what people with diabetes in the UK need to know

Introduction

As vaping has become more common in Great Britain — now exceeding cigarette smoking for the first time in 2026 — understanding the metabolic effects of e‑cigarettes is increasingly important for people with diabetes. This article summarises the latest evidence (including analyses reported late 2025), explains how nicotine can affect insulin absorption and glycaemic control, and offers practical, evidence‑based guidance for people living with diabetes in the UK.

Key concepts

What we mean by insulin absorption and glycaemic control

Insulin absorption describes how quickly and effectively injected insulin (or naturally secreted insulin) enters the bloodstream and acts on tissues. Glycaemic control refers to how well blood glucose is kept within target ranges over time — commonly measured by self‑monitoring and by HbA1c.

Nicotine and non‑nicotine e‑liquids

Most research distinguishes between nicotine‑containing e‑cigarette aerosols and nicotine‑free liquids. Nicotine is an active compound with several physiological effects, whereas other e‑liquid ingredients may have different or minimal direct metabolic effects.

What the evidence says (summary of recent findings)

Key points from recent studies and reviews:

• Population analyses (late 2025): Large US survey analyses reported late in 2025 found an association between e‑cigarette use and a small increase in the risk of prediabetes — roughly a 7% higher prevalence among vaping‑only users in these analyses.
• Animal and controlled exposure studies: Multiple animal experiments and controlled human exposures have shown that aerosol from nicotine‑containing e‑cigarettes can impair insulin tolerance and slow the decline in blood glucose after an insulin challenge. Nicotine‑free e‑liquids often do not produce the same effect in these models.
• Observational human data are mixed: Some large cohort analyses based on NHANES (a US health survey) report little or no clear difference in insulin resistance across different user groups, while other population studies and biomarker analyses indicate that higher nicotine exposure — measured by cotinine — is associated with modestly higher HbA1c and markers of insulin resistance.

Biological mechanisms — how nicotine may affect glucose and insulin

Several plausible mechanisms can explain observed associations:

• Activation of stress pathways: Nicotine stimulates the sympathetic nervous system, increasing adrenaline (and noradrenaline). This can raise blood glucose by promoting glycogen breakdown and reducing insulin sensitivity.
• Direct effects on pancreatic beta cells: Experimental studies suggest nicotine may influence insulin secretion and beta‑cell function, which can alter endogenous insulin responses.
• Peripheral insulin resistance: Nicotine has been shown to impair glucose uptake in peripheral tissues (muscle and fat) in animal and controlled human studies, slowing the decline in blood glucose after insulin administration.

Taken together, these mechanisms explain why nicotine — whether from cigarettes or e‑cigarettes — could make blood glucose harder to control and complicate insulin dosing.

What UK diabetes information services say

UK diabetes information services (including Breakthrough T1D, Diabetes.co.uk and NHS Scotland/MyDiabetesMyWay) currently conclude that there is limited strong clinical trial evidence specifically in people with diabetes, but they warn that nicotine from vaping is likely to raise blood glucose and make glucose management more difficult. Their guidance emphasises caution, especially for people using insulin or with brittle glycaemic control.

Public‑health context in 2026

With vaping now more prevalent than smoking in Great Britain, the potential metabolic effects of e‑cigarettes matter to a larger group of nicotine users and people with diabetes. Even modest changes in insulin sensitivity or HbA1c at a population level are important when more people are exposed.

Practical guidance for people with diabetes

If you live with diabetes or care for someone who does, consider these practical points:

• Discuss vaping with your clinical team: If you vape or are thinking about vaping, mention this at diabetes appointments. Individual risk varies with nicotine dose, frequency of use and your current glucose control.
• Use vaping primarily as a smoking‑cessation aid under supervision: UK guidance generally supports vaping as a less‑harmful alternative to smoking when used to quit cigarettes, but it should be part of a structured cessation plan and clinical oversight if you have diabetes.
• Monitor more closely after changes: If you start, stop or change nicotine dose (including switching to nicotine‑free liquids), check blood glucose more frequently for several days to weeks and adjust insulin or medications only in consultation with your healthcare team.
• Consider nicotine dose: The metabolic effects appear linked to nicotine exposure. Some products are low‑nicotine or nicotine‑free; others are sold with nicotine shots you can add. For example, some longfill products are advertised as 0mg but are supplied with free 20mg nicotine shots that will create a nicotine‑containing e‑liquid when mixed (Crystalize Bar Salts 120ml longfill (with nicotine shots), Crystalize Bar Salts 60ml longfill (with nicotine shots)), while some low‑strength options exist (0.5mg Tick Tock nicotine candy).
• Prefer nicotine‑free options if advised: If your clinician advises avoiding nicotine, nicotine‑free e‑liquids may have less direct impact on insulin sensitivity, though other health considerations remain.
• Know when to seek urgent help: Severe or unexplained hyperglycaemia, frequent hypoglycaemia after starting or stopping vaping, or symptoms of diabetic ketoacidosis warrant immediate medical attention.

Limitations and evidence gaps

Significant gaps remain. Long‑term randomised trials in people with diabetes are lacking, and study results vary by product, nicotine dose, duration and study design. Observational studies can show associations but cannot confirm cause and effect. For these reasons, guidance stresses a cautious, personalised approach.

Conclusion

Evidence up to 2026 suggests nicotine from e‑cigarettes can raise blood glucose and interfere with insulin action in experimental settings, and population analyses raise concern about a small increase in prediabetes risk. Human observational studies are mixed, but biomarker data linking cotinine to higher HbA1c provide biological plausibility. For people with diabetes in the UK, the prudent approach is to discuss vaping with your diabetes team, use vaping primarily as a supervised smoking‑cessation tool if needed, monitor blood glucose closely when changing nicotine exposure, and favour nicotine‑free options only if recommended by your clinician. Ongoing research and better trials are needed to give firmer guidance, but current evidence supports careful, individualised management rather than assuming vaping is metabolically harmless.